Dems’ likely Senate gains

When the dust settles this November, chances are Democrats will be in charge. Not only is Barack ObamaBarack Hussein ObamaOvernight Energy: EPA declines to write new rule for toxic spills | Senate blocks move to stop Obama water rule | EPA bought 'tactical' pants and polos Clarifying the power of federal agencies could offer Trump a lasting legacy Dems allow separation of parents, children to continue, just to score political points MORE likely to be the next president, but the Democratic House advantage — currently 36 seats — is seemingly certain to grow to a margin of at least 50.

But the success or failure of the Democratic majority’s agenda will ultimately be determined in the Senate, where Republicans are struggling to retain enough seats to block the Democratic mandate via filibuster.

Democrats currently hold 49 Senate seats, and enjoy the solid support of Vermont Independent Bernie SandersBernard (Bernie) SandersBernie Sanders: Trump thinks like an authoritarian Democrats protest Trump's immigration policy from Senate floor Trump's America fights back MORE. Joe Lieberman (I-Conn.) initially gave Democrats their 51st seat for the majority, but has since ended up embracing the GOP on many key issues. Still, Republicans are faring so poorly this year that they face an outside chance of falling below 41 seats. That would mean no filibusters — and that would end the GOP’s ability to stymie the Democratic agenda.

Democrats have a near-guaranteed pickup in Virginia and likely pickups in Alaska, Colorado, New Mexico and New Hampshire. Those five seats would bring the Democratic Conference to 55 seats. Democrats are running neck and neck against incumbent Republicans in Minnesota, North Carolina and Oregon. And they lag only slightly in Mississippi’s special-election seat.

If Democrats win those four attainable races, they’d reach 59 seats. That’s not a filibuster-proof majority, but large enough to reach 60 on an issue-by-issue basis. Senators like Maine’s Susan CollinsSusan Margaret CollinsSenate Gang of Four to meet next week on immigration Republicans agree — it’s only a matter of time for Scott Pruitt Skyrocketing insulin prices provoke new outrage MORE and Olympia Snowe, Arlen Specter of Pennsylvania, George Voinovich of Ohio and even Lieberman would likely defect frequently to the Democratic positions on issues of healthcare, labor, national security and energy.

But even if Democrats don’t reach 60 this year, their chances in 2010 are excellent. In fact, the 2010 map looks even better for Democrats than this year’s.

Sen. Sam Brownback of Kansas is retiring, and popular Democratic Gov. Kathleen SebeliusKathleen SebeliusMr. President, let markets help save Medicare IRS Tax Day glitch exposes antiquated tech infrastructure Trump administration's reforms could make welfare work again MORE will be available to make a run at the seat. Kentucky’s Jim Bunning barely escaped alive four years ago. Whether he retires or not, Rep. Ben Chandler (D) will be the favorite in 2010. New Hampshire Sen. Judd Gregg’s (R) conservatism is increasingly out of step with his state, which has been systematically cleansing itself of all things Republican. Watch for Rep. Paul Hodes (D) to challenge him.

In Ohio, Voinovich will have no shortage of Democrats looking for a sequel to the 2006 ouster of Republican incumbent Mike DeWine. And in Alabama, expect wildly popular Agricultural Commissioner Ron Sparks to challenge incumbent Sen. Richard Shelby (R). Sparks already regrets passing on this year’s Senate race, and won’t likely make the same mistake twice.

Moreover, rumors are swirling that Iowa’s Chuck GrassleyCharles (Chuck) Ernest GrassleyGrassley wants to subpoena Comey, Lynch after critical IG report Senate Dems call for Judiciary hearing on Trump's 'zero tolerance' Republicans agree — it’s only a matter of time for Scott Pruitt MORE (R) might retire.

Freshman Republicans will face challenges in Alaska, Florida, Georgia, North Carolina, Oklahoma, South Carolina and South Dakota. Some of those challenges will be tougher than others, of course, but elected officials are most vulnerable during their first reelection battle, and Democrats will aggressively pursue these seats.

Even in Arizona, polling in 2007 suggested that popular Democratic Gov. Janet Napolitano could defeat longtime incumbent John McCainJohn Sidney McCainDon’t disrespect McCain by torpedoing his clean National Defense Authorization Act Meghan McCain rips Trump's 'gross' line about her dad Trump's America fights back MORE (R) in a battle of titans. And in Louisiana, Sen. David VitterDavid Bruce VitterSenate panel advances Trump nominee who wouldn't say if Brown v. Board of Education was decided correctly Planned Parenthood targets judicial nominee over abortion comments Trump nominates wife of ex-Louisiana senator to be federal judge MORE’s (R) sordid dalliances with prostitutes may provide an unexpected opening in a state that has been trending away from Democrats.

For their part, Democrats may have to sweat tricky reelection efforts in Colorado and Arkansas.

But barring any unexpected retirements or vacancies, 2010 — like 2008 — will be played almost exclusively on red territory.

The filibuster-proof majority is certainly within reach of Democrats — if not in this cycle, then in the next.

Moulitsas is founder and publisher of Daily Kos .