Retirements always pose a threat to congressional majorities. Before he took the helm of the Senate Democratic campaign committee in 2005, Sen. Chuck SchumerCharles SchumerDemocrats urge Trump to condemn Charlottesville violence Melania Trump on Charlottesville protests: 'No good comes from violence' It's time for McConnell to fight with Trump instead of against him MORE (D-N.Y.) told then-Minority Leader Harry ReidHarry ReidOPINION | 5 ways Democrats can win back power in the states THE MEMO: Trump's base cheers attacks on McConnell It's time for McConnell to fight with Trump instead of against him MORE (D-Nev.), "We can't let red-state Democrats retire — in '04 we lost every race where they did."

Reid agreed; Schumer subsequently won back the majority in the 2006 cycle and later helped boost the Democratic majority to 60 seats.

The Schumer-Reid exchange was detailed in Schumer's book titled, "Positively American: Winning Back the Middle-Class Majority One Family at a Time."

The Democrats who are retiring do not all hail from red states. Sen.Kent Conrad (D-N.D.) does, and Republicans are heavily favored to pick up that seat.

Republicans are also favored to win Sen. Jim Webb's (D) seat in Virginia, and their chances increase if former Virginia Gov. Tim KaineTim Kaine Violent white nationalist protests prompt state of emergency in Virginia Republicans will get their comeuppance in New Jersey, Virginia Spicer signs deal with top TV lawyer: report MORE (D) opts not to run.

Sen. Joe Lieberman (I-Conn.) is also not running for reelection. Democrats are confident they can win in this blue state, especially in a presidential election year. But in all likelihood, they will have to fight for it.

Both parties will aggressively vie for Bingaman's seat. Obama won the purple state in 2008 and George W. Bush triumphed there in 2004.

Ross K. Baker, a political scientist at Rutgers University, said, "Parties in Congress, like armies in the field, suffer casualties in two ways: They are lost in election battles and they are pulled out of the line from combat fatigue after the elections are over. The Democrats have sustained both forms of loss. The combat fatigue casualties have sized up the bloody conflicts ahead on the budget, debt extension, and entitlements and have requested to be evacuated to the rear area."

He added, "This is an ominous sign for the slender Democratic majority that can berescued only with a smashing victory at the presidential level. Obama has shown he can provide coattails and he may have to do so again."

Democrats got some good news this week when Senate Minority Whip Jon Kyl (R-Ariz.) announced he would not run for a fourth term. But on Friday, Homeland Security Secretary Janet Napolitano, a former governor of Arizona, ruled out a bid.

While the retirements of the three Democrats and Lieberman have attracted many headlines and boosted the GOP's confidence, the early announcements give Democrats ample time to find strong candidates.

Sen. Patty MurrayPatty MurrayCBO to release report Tuesday on ending ObamaCare insurer payments OPINION | Progressives, now's your chance to secure healthcare for all McConnell open to bipartisan deal on health insurance payments MORE (Wash.), who heads the Democratic Senatorial Campaign Committee, has been pushing Democratic senators up for reelection in 2012 to make up their minds early in the cycle.

Republicans picked up seven seats in the 2010 cycle, including Sen. Scott Brown's (R-Mass.) win in January last year.

Democrats are targeting Brown, who faces another tough election next year. They are also targeting Sen. John Ensign (R-Nev.), whose ethics controversies pose a major obstacle to winning a third term. Republican operatives note that Brown has a $7.2 million campaign war chest and Ensign will likely face a primary challenge.

Democratic incumbents who face reelection next year include Jon TesterJon TesterWhy 'cherry-picking' is the solution to our nation’s flood insurance disaster Trump signs Veterans Affairs bill at New Jersey golf club It's time for McConnell to fight with Trump instead of against him MORE (Mont.), Joe ManchinJoe ManchinOPINION | 5 ways Democrats can win back power in the states Trump's Democratic tax dilemma Manchin eyed as potential pick for Energy secretary: report MORE (W.Va.), Sherrod BrownSherrod Campbell BrownOvernight Finance: House passes spending bill with border wall funds | Ryan drops border tax idea | Russia sanctions bill goes to Trump's desk | Dems grill bank regulator picks Dems grill Trump bank regulator nominees Senate Dems launch talkathon ahead of ObamaCare repeal vote MORE (Ohio), Ben Nelson (Neb.), Bill NelsonClarence (Bill) William NelsonThe five kinds of Republicans who could primary Trump Overnight Tech: Senate confirms two FCC commissioners | Dems want more time on net neutrality | Tech groups push White House on 'startup visa' Senate confirms two new FCC commissioners MORE (Fla.), Debbie StabenowDebbie StabenowHead of McConnell-backed PAC: We're 'very interested' in Kid Rock Senate campaign Juan Williams: Trump and the new celebrity politics Senate Dems unveil trade agenda MORE (Mich.) and Claire McCaskillClaire McCaskillSenators push for possible FCC enforcement over Lifeline fraud Democrat senator: Trump has elevated Kim Jong-Un to the world stage It's time for McConnell to fight with Trump instead of against him MORE (Mo.).

Republicans need to win a net of at least three seats to control the Senate (four if Obama wins reelection).


This article was updated at 2:58 p.m.