History argues for Democratic Senate gains

History argues for Democratic Senate gains
© Greg Nash

Senate Democrats have one enormous advantage even as they face one of the most difficult political terrains in recent memory: They are not the party that controls the White House.

A new analysis of election results over the past 10 midterm cycles underlines that since 1978, incumbents of the party out of power, even in states the president carried in the previous election, are overwhelmingly likely to win another six-year term.

This is true, the analysis states, even in states where the president cruised to reelection.

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In states that went for the president by more than 10 percentage points, the other party’s senator has won reelection in the following midterm more than 90 percent of the time.

Over that period, 43 senators have run for reelection in states the other party’s president won by more than 10 percentage points. Only four — Max Cleland (D-Ga.) in 2002, Al D’Amato (R-N.Y.) in 1998, Howard Cannon (D-Nev.) in 1982 and Edward Brooke (R-Mass.) in 1978 — lost their reelection bids.

Such statistics are of crucial interest given this year’s Senate map, in which 10 Democratic incumbents will run for reelection in states President TrumpDonald John TrumpCould Donald Trump and Boris Johnson be this generation's Reagan-Thatcher? Merkel backs Democratic congresswomen over Trump How China's currency manipulation cheats America on trade MORE won in 2016.

“Every midterm, it’s always good to be the party out of the White House,” said Bruce Mehlman, a Republican lobbyist who analyzed the 333 Senate races that have taken place since 1978 as part of a widely-read quarterly political update to clients.

Five Democratic senators are running for reelection in states Trump won by more than 10 points: Sens. Joe DonnellyJoseph (Joe) Simon DonnellyTrump nominees meet fiercest opposition from Warren, Sanders, Gillibrand GOP frets over nightmare scenario for Senate primaries McConnell's Democratic challenger McGrath backtracks on Kavanaugh comments MORE (Ind.), Claire McCaskillClaire Conner McCaskillTrump nominees meet fiercest opposition from Warren, Sanders, Gillibrand Feds allow campaigns to accept discounted cybersecurity services GOP frets over nightmare scenario for Senate primaries MORE (Mo.) and Heidi HeitkampMary (Heidi) Kathryn HeitkampTrump nominees meet fiercest opposition from Warren, Sanders, Gillibrand McConnell's Democratic challenger McGrath backtracks on Kavanaugh comments McConnell's Democratic challenger says she likely would have voted for Kavanaugh MORE (N.D.) are among the most vulnerable members seeking reelection. Sens. Joe ManchinJoseph (Joe) ManchinPoll: McConnell is most unpopular senator Dems open to killing filibuster in next Congress Trump nominees meet fiercest opposition from Warren, Sanders, Gillibrand MORE (W.Va.) and Jon TesterJonathan (Jon) TesterPoll: McConnell is most unpopular senator Trump nominees meet fiercest opposition from Warren, Sanders, Gillibrand The Hill's 12:30 Report: Pelosi looks to squash fight with progressives MORE (Mont.) are seen as safer bets, though their wins are by no means assured.

Five other Democrats are running for reelection in states Trump won by fewer than 10 points: Sens. Tammy BaldwinTammy Suzanne BaldwinThe Hill's Morning Report: Trump walks back from 'send her back' chants Overnight Health Care — Presented by PCMA — Health care moves to center stage of Democratic primary fight | Sanders, Biden trade sharps jabs on Medicare for All | Senate to vote on 9/11 bill next week | Buttigieg pushes for cheaper insulin The Hill's Morning Report - Trump seizes House impeachment vote to rally GOP MORE (D-Wis.), Sherrod BrownSherrod Campbell BrownThe Hill's Morning Report - A raucous debate on race ends with Trump admonishment On The Money: Senators unload on Facebook cryptocurrency | Tech giants on defensive at antitrust hearing | Democrats ask Labor Department to investigate Amazon warehouses Hillicon Valley: Senators unload on Facebook cryptocurrency plan | Trump vows to 'take a look' at Google's ties to China | Google denies working with China's military | Tech execs on defensive at antitrust hearing | Bill would bar business with Huawei MORE (Ohio), Bob CaseyRobert (Bob) Patrick CaseyDemocrats grill USDA official on relocation plans that gut research staff Trump's new labor chief alarms Democrats, unions Hillicon Valley: Lawmakers struggle to understand Facebook's Libra project | EU hits Amazon with antitrust probe | New cybersecurity concerns over census | Robocall, election security bills head to House floor | Privacy questions over FaceApp MORE Jr. (Pa.), Bill NelsonClarence (Bill) William NelsonDemocrats target Florida Hispanics in 2020 Poll: Six Democrats lead Trump in Florida match-ups How Jim Bridenstine recruited an old enemy to advise NASA MORE (Fla.) and Debbie StabenowDeborah (Debbie) Ann StabenowDemocrats grill USDA official on relocation plans that gut research staff USDA expected to lose two-thirds of research staff in move to Kansas City GOP Senate challenger in Michigan raises .5 million in less than a month MORE (Mich.). Of those five, only Nelson has a top-tier challenger, in Florida Gov. Rick Scott (R).

If history holds, all five of those senators will be back for another six-year term. In the last 10 midterms, no senator seeking reelection from a state the other party’s president won by fewer than 10 percentage points has lost.

Incumbents from the party out of power have a better chance of winning reelection than incumbents from the same party that holds the White House, Mehlman found.

Just about half of members of a president’s party win reelection in states the president did not carry. Over the last 40 years, the incumbent of a president’s party has won reelection in 14 of 27 attempts in a state the president did not carry.

This year, only one Republican — Sen. Dean HellerDean Arthur HellerThis week: Barr back in hot seat over Mueller report Trump suggests Heller lost reelection bid because he was 'hostile' during 2016 presidential campaign Trump picks ex-oil lobbyist David Bernhardt for Interior secretary MORE (R-Nev.) — falls into that category. But Trump lost Nevada to Hillary ClintonHillary Diane Rodham ClintonPoll: Majority of Democratic voters happy with their choices among 2020 contenders No presidential candidate can unite the country GOP lawmakers speak out against 'send her back' chants MORE by just 2.5 percentage points, and the incumbent senator has won nearly 69 percent of the time if their party’s president lost by such a narrow margin.

The president’s party has held 80 percent of open seats in states he carried by more than 10 points over the last 10 midterms, but just 31 percent of seats that the president carried by less than a 10-point margin. This year, that means Republicans have a strong chance to retain Sen. Bob CorkerRobert (Bob) Phillips CorkerTrump announces, endorses ambassador to Japan's Tennessee Senate bid Meet the key Senate player in GOP fight over Saudi Arabia Trump says he's 'very happy' some GOP senators have 'gone on to greener pastures' MORE’s (R-Tenn.) seat, but they have a far weaker chance of holding on to Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeFlake urges Republicans to condemn 'vile and offensive' Trump tweets Flake responds to Trump, Jimmy Carter barbs: 'We need to stop trying to disqualify each other' Jeff Flake responds to Trump's 'greener pastures' dig on former GOP lawmakers MORE’s (R-Ariz.) seat in a state Trump carried by only 4 percentage points.

“It’s better to be a Democratic incumbent in a state Trump won by more than 10 than a Republican open seat candidate in a state Trump won by less than 10,” Mehlman said.