Republicans face an uphill road to keeping their Senate majority in the November election.
They must fight to protect 24 GOP-held seats, while the Democrats have to worry about only 10.
Here are the top 10 seats likely to flip, nine of which are held by Republicans.
Sen. Mark KirkMark Steven KirkDuckworth announces reelection bid Brave new world: Why we need a Senate Human Rights Commission Senate majority battle snags Biden Cabinet hopefuls MORE (R-Ill.) is running in a state that President Obama won by 17 and 25 percentage points in 2012 and 2008, respectively. The political makeup of the state makes him the most vulnerable incumbent, according to strategists in both parties.
Hillary ClintonHillary Diane Rodham ClintonClinton lawyer's indictment reveals 'bag of tricks' Attorney charged in Durham investigation pleads not guilty Attorney indicted on charge of lying to FBI as part of Durham investigation MORE, the front-runner for the Democratic nominee, grew up in Illinois and won the state's Democratic primary with more than 50 percent of the vote.
While GOP-allied outside groups are spending heavily in various Senate battleground states, they’re not doing so in Illinois, a troubling sign for Kirk.
His opponent, Rep. Tammy Duckworth (Ill.), was the Democrats’ top recruit, although she has run into some turbulence of her own.
Duckworth has been accused by two former employees of the state’s Department of Veterans Affairs of retaliating against them while she headed the agency. A trial date has been set for Aug. 15.
Sen. Ron JohnsonRonald (Ron) Harold JohnsonDomestic extremists return to the Capitol GOP senator: Buying Treasury bonds 'foolish' amid standoff over debt ceiling, taxes Internal poll shows Barnes with 29-point lead in Wisconsin Democratic Senate primary MORE (R-Wis.) is viewed as the second most vulnerable incumbent.
He faces a strong opponent in former Sen. Russ Feingold (D-Wis.), whom he defeated in 2010, a Republican wave year that was fueled by a national backlash against ObamaCare.
A WPR/St. Norbert poll from late April showed Feingold leading by 10 points.
Obama won the state by 7 and 14 percentage points in 2012 and 2008, respectively.
Unlike Kirk, Johnson has done little to tack to the center or position himself as a moderate. Some Senate GOP strategists privately wonder if he began preparing for this race early enough.
But Johnson has backing from outside groups. The U.S. Chamber of Commerce is on the air in Wisconsin, according to a strategist familiar with advertising buys.
Senate Republicans have stepped up their efforts to persuade Sen. Marco RubioMarco Antonio RubioMilley says calls to China were 'perfectly within the duties' of his job Overnight Defense & National Security — Milley becomes lightning rod Joint Chiefs Chairman Milley becomes lightning rod on right MORE (R-Fla.) to change his mind and run for reelection, a sign they’re not confident in their ability to otherwise hold his seat.
McConnell says he is “doing everything” to get Rubio to run.
He might be able to clear the field. Otherwise, four Republican candidates will battle for the nomination up until the Aug. 30 primary: Lieutenant Gov. Carlos Lopez-Cantera, Rep. Ron DeSantis, Rep. David Jolly and multi-millionaire homebuilder Carlos Beruff.
A Quinnipiac poll from early May showed the likely Democratic nominee, Rep. Patrick Murphy, leading DeSantis, Jolly and Lopez-Cantera by margins ranging from 1 to 3 percentage points.
Obama carried the state in 2008 and 2012, where Democrats have a 262,000-person advantage in voter registration, according to the Department of State’s division of elections.
A Mason-Dixon poll released last week showed Hillary Clinton leading Trump by 3 points in the state.
Democrats have their own primary to worry about. Rep. Alan GraysonAlan Mark GraysonFlorida Rep. Val Demings officially enters Senate race against Rubio Demings raises Democrats' hopes in uphill fight to defeat Rubio Demings planning to run for Senate instead of Florida governor MORE has embraced Democratic presidential candidate Bernie SandersBernie SandersSunday shows preview: Coronavirus dominates as country struggles with delta variant Democrats urge Biden to commute sentences of 4K people on home confinement Briahna Joy Gray: Push toward major social spending amid pandemic was 'short-lived' MORE and is trying to outflank Murphy from the left.
But Senate Minority Leader Harry ReidHarry Mason ReidDemocrats say Biden must get more involved in budget fight Biden looks to climate to sell economic agenda Justice Breyer issues warning on remaking Supreme Court: 'What goes around comes around' MORE (D-Nev.) has thrown his weight behind Murphy, who reported $5.6 million cash on hand at the end of March.
4. New Hampshire
New Hampshire hasn’t voted for a Republican presidential candidate since 2000, when George W. Bush carried the state, and Sen. Kelly AyotteKelly Ann AyottePoll: Potential Sununu-Hassan matchup in N.H. a dead heat Democrats facing tough reelections back bipartisan infrastructure deal Sununu seen as top recruit in GOP bid to reclaim Senate MORE (R) faces a highly touted Democratic challenger in sitting Gov. Maggie Hassan.
Ayotte is a formidable candidate herself, though, and considered a rising star in the Senate. She has differentiated herself from her party by supporting Obama’s effort to curb carbon emissions from power plants, which affects New Hampshire disproportionately because of prevailing wind patterns.
Outside groups are spending heavily in the state. The Senate Majority PAC, a Democratic group dedicated to flipping the upper chamber, now has a $1 million television campaign focused on the Boston media market.
The U.S. Chamber is on the air helping Ayotte.
Hassan is trying to use Trump to her advantage by insisting her opponent will “need to be held accountable for his statements.”
Republicans are highlighting the number of days Hassan has spent out of the state fundraising for her campaign.
Pennsylvania Sen. Pat Toomey (R) has tried to portray himself as a moderate to voters by championing legislation with Democratic Sen. Joe ManchinJoe ManchinBriahna Joy Gray: Push toward major social spending amid pandemic was 'short-lived' Overnight Energy & Environment — Presented by Climate Power — Emissions heading toward pre-pandemic levels Biden discusses agenda with Schumer, Pelosi ahead of pivotal week MORE (W.Va.) in the last Congress to expand background checks for firearms.
Toomey presents himself as a soft-spoken, reasonable conservative, drawing a contrast with fire-breathing Tea-Party candidates who turn off most voters in Pennsylvania.
But he will have to overcome a lot of history to keep his seat. Obama won Pennsylvania by 5 and 10 points in 2012 and 2008, respectively. A Republican presidential candidate hasn’t won the state since 1988.
There are 4 million registered Democrats in the state, compared to 3.1 million registered Republicans, according to Pennsylvania’s Department of State.
Toomey, however, is seen as having a weaker opponent than Ayotte in New Hampshire or Sen. Rob PortmanRobert (Rob) Jones PortmanEmboldened Trump takes aim at GOP foes Overnight On The Money — Presented by Wells Fargo — GOP senator: It's 'foolish' to buy Treasury bonds Senate lawmakers let frustration show with Blinken MORE (R) in Ohio.
The Democratic Senatorial Campaign Committee and allied outside groups spent $4.86 million to help Katie McGinty win the Democratic primary over former Rep. Joe Sestak.
McGinty is now dealing with a controversy over her claim that she was the first member of her family to go to college, even though records show her older brother graduated well before she matriculated.
Portman has a significant cash advantage over his Democratic rival, former Gov. Ted Strickland (D), and strategists rate him a better candidate overall.
Republicans say Strickland takes a sometimes lackadaisical approach to the campaign and predict Portman will outwork him.
Portman reported $13.4 million in cash on hand at the end of March, compared to Strickland’s $2.7 million.
Portman served as U.S. trade ambassador under George W. Bush, a potential liability in a state hit hard by globalization and the loss of domestic manufacturing.
He has tried to inoculate himself from attacks by opposing the Trans-Pacific Partnership, an accord with 11 other nations representing the largest trade deal in U.S. history.
Portman won a coup last week when the United Mine Workers of America endorsed him. It was an embarrassment for Strickland, who represented Ohio’s coal country in Congress.
Portman is considered slightly safer than Ayotte and Toomey because Ohio has voted Republican more frequently in presidential elections. George W. Bush carried it twice before Obama won it in 2008 and 2012.
A Quinnipiac poll released May 10 showed Trump with a 4-point lead over Clinton in Ohio.
Both sides will spend heavily in this presidential battleground state. Senate Majority PAC has spent $2.6 million to date and has reserved $9.5 million for the fall.
Portman this week launched three new television ads with a $15 million media buy.
Freedom Partners Fund, a conservative advocacy group, is also on the air in Ohio, according to a strategist who tracks media buys.
The seat held by retiring Senate Democratic Leader Harry Reid is the only Democratic one in the top 10 most likely to flip.
Republicans have a strong candidate in Rep. Joe Heck, whose district covers southern Las Vegas and Henderson — a swing portion of the state.
Obama won Heck’s 3rd Congressional District, which has a large Hispanic population, by 9 points in 2008 and tied Mitt Romney there in 2012.
The Republican thinking is that if Heck wins his own district and the 2nd Congressional District in northern Nevada, where Republicans have a historic advantage, he’ll be in good shape to capture Reid’s seat.
But Trump and his poor numbers with Hispanic voters is likely to be more of a liability for Heck than for most other Senate GOP candidates because of Nevada’s heavy concentration of Hispanic voters.
“It’s certainly going to be toxic. It’s only the level of toxicity that’s going to be the question,” said longtime Nevada political commentator Jon Ralston about Trump’s impact on Heck.
Reid’s fabled Democratic machine, which he built over his long career, will be an asset to Democratic candidate Catherine Cortez Masto. She is running to be the first Hispanic woman elected to the Senate, and her campaign message will resonate with Clinton’s quest to be the first female commander in chief.
8. North Carolina
Former state Rep. Deborah Ross (D) emerged from relative obscurity in North Carolina, but she’s trying to turn that to her advantage in what is widely perceived to be the year of the outsider candidate.
She surprised observers by out-raising Sen. Richard BurrRichard Mauze BurrEmboldened Trump takes aim at GOP foes NC Republican primary key test of Trump's sway The 19 GOP senators who voted for the T infrastructure bill MORE (R), who has served in Congress since 1995, in the first three months of the year. She collected $1.3 million to his $1.1 million.
But GOP strategists say Ross hasn’t been battle tested, and her numbers are likely to come down once the campaign heats up in earnest.
North Carolina is trending Democratic and that’s worrisome for Burr. Obama won the state in 2008 although Romney carried it narrowly in 2012.
The surprise emergence into a national political issue of North Carolina’s bathroom law — which restricts transgendered people’s choice of bathroom — has roiled the race.
Burr initially said the state proposal did not discriminate, but more recently he has criticized it as “too expansive” and called for it to be rolled back.
The difficulty in assessing how the issue plays politically reflects the fast-evolving politics of the state.
Trump has a four-point lead over Clinton, according to two recent polls, but she is expected to target the state in the fall.
North Carolina is 21 percent African-American and almost 9 percent Hispanic, and Democrats will try to use Trump’s sometimes heated rhetoric to push minority voters to back Clinton.
Trump and his low approval rating among Hispanic voters hurts Sen. John McCainJohn Sidney McCain20 years after 9/11, US foreign policy still struggles for balance What the chaos in Afghanistan can remind us about the importance of protecting democracy at home 'The View' plans series of conservative women as temporary McCain replacements MORE more than any other Senate Republican candidate.
Twenty-two percent of the state’s eligible voters are Hispanic, and the number is likely to be higher come Election Day. Democrats say Hispanics are registering in greater numbers to vote against Trump, and given that 31 percent of the state’s population is Hispanic, there’s lots of room to grow the rolls.
McCain has a tough opponent in Rep. Ann KirkpatrickAnn Kirkpatrick Ariz. state senator who saved Gabby Giffords's life ends congressional bid due to COVID-19 surge Democrats fret over Trump-district retirements ahead of midterms Democratic Rep. Ron Kind won't seek reelection in Wisconsin MORE (D), whose congressional district covers a huge rural swath in the northeast. She reported $1.3 million in cash on hand at the end of March, compared to McCain, who reported $5.5 million.
McCain knows he’s in a tough fight, but he faces a tricky spot because publicly rejecting Trump could hurt him among Republican voters, who supported him overwhelmingly in the presidential primary. At the same time, he needs to be mindful of the growing Hispanic electorate.
McCain is helped by a public name identification of close to 100 percent after serving nearly five terms in the upper chamber. His allies say his political persona is well established and predict he won’t have difficulty standing apart from Trump.
Bill ClintonWilliam (Bill) Jefferson ClintonBusiness coalition aims to provide jobs to Afghan refugees Biden nominates ex-State Department official as Export-Import Bank leader Obamas, Bushes and Clintons joining new effort to help Afghan refugees MORE was the last Democratic presidential candidate to carry the state, in 1996.
Democrats are bullish on their recruit, Jason Kander, Missouri’s secretary of state. While he is viewed as a talented candidate, he is running in a very Republican state.
But Senate Democratic candidates have won in Missouri before, and the conditions in 2012 are promising for a repeat.
Kander outraised Sen. Roy BluntRoy Dean BluntGOP hopes spending traps derail Biden agenda A tale of two chambers: Trump's power holds in House, wanes in Senate The Hill's Morning Report - Presented by AT&T - Senate passes infrastructure bill, budget resolution; Cuomo resigns MORE, the Republican incumbent, in the first quarter of this year, $1.3 million to $1.25 million. Blunt has served in Congress since 1997, when he was elected to the House, and in the Senate since 2010.
He is not as entrenched an incumbent as McCain, but Missouri is 80 percent white and has a small Hispanic population of less than 4 percent. Trump’s incendiary rhetoric is not likely to have as much of an effect here as in other states.
Blunt does have to contend with the anti-establishment, anti-Washington winds that have roiled the presidential primaries. He is a member of the Senate Republican leadership and served as majority leader in the House.
He has developed a track record as a pragmatic dealmaker in Congress, something that could help win over voters frustrated with Washington gridlock. He recently put together a deal with Sen. Patty MurrayPatricia (Patty) Lynn MurrayConservation group says it will only endorse Democrats who support .5T spending plan Support the budget resolution to ensure a critical investment in child care Senate Democrats try to defuse GOP budget drama MORE (D-Wash.) to provide $1.1 billion in emergency funds to fight the Zika virus.
Democrats are going to hit Blunt on his ties to lobbyists. His wife is a lobbyist for Kraft Foods, and three of his kids have worked in the industry.
“His whole family is lobbyists,” said a Democratic strategist.
Missouri has voted consistently for Republican presidential candidates in recent years, but the Clintons have a history of success here. Bill Clinton won the state in 1992 and 1996.
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