Republicans fight to reclaim the Senate majority: 2012 races to watch

— -- Winning a majority in the U.S. Senate in 2012 was never going to be easy for Republicans. But over the past several months, new obstacles have continued to stack up as a few seemingly locked-up Senate races have become less than sure for the GOP. And given the Democrats' success in recruiting popular candidates to run, the Republicans are working overtime to catch up and turn their own challengers into strong general election contenders. They need to gain four seats to take control of the upper chamber.

"There's been a lot of turbulence for Republicans," the Democratic Senatorial Campaign Committee communications director Matt Canter told Yahoo News, noting the difficulties Republicans have had recruiting candidates.

One major setback occurred  when Republican Sen. Olympia Snowe of Maine announced her surprise retirement in February. As one of the least conservative Republicans in the Senate, running in a heavily independent state, Snowe was a virtual shoe-in for re-election. Now her seat is up for grabs.

Currently, Republicans hold 47 seats in the Senate to the Democrats' 51, including Independent Bernie Sanders of Vermont and Independent Democrat Joe Lieberman of Connecticut. Only 10 Republicans are up for re-election this year, compared to 23 Democrats (counting Lieberman and Sanders, who caucus with the party). But Democratic recruiting successes have kept several of the open seats and contested races in play.

On the other side of the spectrum are the tea party candidates, who Democrats argue have hurt the Republicans by waging fierce primary battles--and even winning some of them.

"The impact of the tea party has been felt in almost every single Senate race in the country," Canter of the DSCC said to Yahoo News. "The seeds have been sowed, but I don't think we've seen the full impact yet. … We're going to see a lot more fireworks before the dust settles."

Republicans insist that this year's slate of top tea party candidates are strong general-election contenders. "Primaries are only a problem if the person who is nominated is not the winner in the general election," Brian Walsh, the National Republican Senatorial Committee communications director, told Yahoo News.

Walsh cited North Dakota, Nebraska, Missouri and Montana as states where President Barack Obama's low approval ratings will help the Republican candidates running for the Senate. Both Walsh and Canter named Virginia's race as the one where the presidential contest will have the greatest influence.

A Republican strategist, who wished to remain anonymous when speaking about strategy details, noted to Yahoo News that Republican odds will depend heavily on three key races: Maine, Massachusetts and Nevada.

"We feel best about Nevada," the strategist said of those three contests.

"If we win two out of those three, we can win back a majority," the strategist said. "If we win one, it becomes complicated."

Here are the top Senate races in play this year:

• Maine: Republican Sen. Olympia Snowe's decision to retire unexpectedly turned this Senate seat into one of the year's races to watch, handing Democrats another pickup opportunity. The party is cheering the entry of former Gov. Angus King, an independent, who hasn't yet confirmed with whom he will caucus, although it's presumed he will side with Democrats. In a telling sign, the NRSC has already attacked him as beholden to Washington Democrats and questioned his "independent" label. On the Republican side, the primary is a crowded and chaotic affair with at least six contenders having expressed interest in the race, including former state Sen. Rick Bennett; former town selectman Scott D'Amboise, a tea party favorite and former unsuccessful congressional candidate; state Sen. Debra Plowman as well as other state officeholders. King also faces Democratic competition.

• Massachusetts: Democrats scored a major victory when they convinced consumer advocate Elizabeth Warren to challenge Republican Sen. Scott Brown, who defied the odds in 2010 by winning a special election to succeed Ted Kennedy. Brown remains highly popular in the state and is promoting his bipartisanship ahead of November. Warren brings star power to the ticket as President Barack Obama's first pick to head up the Consumer Financial Protection Bureau. Despite some campaign hiccups, including an ongoing controversy over her Cherokee heritage, polls continue to show the neck-and-neck race within the margin of error.

• Missouri: One major bright spot for Republicans is Democratic Sen. Claire McCaskill's vulnerable re-election bid. Unfortunately for Republicans, their nominee must first weather a competitive primary race which includes Rep. Todd Akin, businessman John Brunner, former state treasurer Sarah Steelman and others. Democrats point out that former Reps. Sam Graves and Jo Ann Emerson, top Republican recruits, both passed on the race, although the GOP says publicly it's pleased with the field. Working in the Republicans' favor is the continued controversy dogging McCaskill. In 2011, it was discovered that she was billing taxpayers to cover the cost of a private plane. Even though she returned the money, Republicans say the damage has been lasting.

• Montana: First-term Democratic Sen. Jon Tester faces a tough re-election battle this fall by virtue of his conservative-leaning state and the fact that it's a presidential election year. Tester has carefully carved out a moderate voting record, but is regarded--even by supporters--as highly endangered. "In Washington, Tester's way is Obama's way," the narrator states in a Crossroads GPS ad attacking the Senator. The national parties have already invested millions in the race, which is shaping up to be a contest between Tester and Republican Rep. Denny Rehberg--the state's lone statewide House member.

• Nebraska: Another major recruiting win for Democrats came when former Gov. Bob Kerrey entered this open seat Senate race. Republicans point out that Kerrey, who previously served as a Senator, is far from a flawless contender. They've labeled him a carpetbagger for living in New York since hanging up his public service hat. But Republicans have their work cut out for them too. Their candidate, state Sen. Deb Fischer, just narrowly clinched the nomination. Fisher is perhaps the least tested major candidate in the race, which each side argues is a positive attribute, depending on how you look at it.

• Nevada: Republicans are fighting to hold onto Nevada this fall with appointed Sen. Dean Heller as their nominee. Democrats say Hispanic voters' distrust of Heller will help Democratic frontrunner Rep. Shelley Berkley. What's more, the party can piggyback upon the groundwork Sen. Harry Reid's successful 2010 re-election bid already built. Meanwhile, Republicans are using Berkley's party label and voting record against her, arguing she votes lockstep with her party leaders while Heller has taken an independent stance on key issues.

• North Dakota: Democrats welcomed former state attorney general Heidi Heitkamp's decision to enter this open seat race. Heitkamp, a former statewide candidate many times over, was her party's top pick to fight to hold onto the seat of retiring Sen. Kent Conrad. She is likely to take on tea party freshman Rep. Rick Berg, who Democrats cast as too extreme and too eager for a promotion to win the general election. Heitkamp is already facing attacks branding her a liberal and tying her to the president, who isn't well-liked in the state.

• Virginia: National strategists from opposing parties agree on little, but both the NRSC and DSCC say that perhaps no other contest this fall will be tied more closely to presidential politics than the Virginia Senate race. Each party recruited a star candidate for this open seat (currently held by moderate Democratic Sen. Jim Webb): Former Democratic Gov. Tim Kaine and former Republican Sen. George Allen, who also served as governor. Virginia remains a major swing state for the presidential race, meaning that the Senate race will likely be fought at the national level. And we've already seen evidence of that in the form of a Joe Biden fundraiser for Kaine and National Rifle Association support for Allen. In the June 12 Republican primary, Allen is expected to emerge victorious.

More popular Yahoo! News stories:

Clinton blasts Russia, says support for Syrian regime could lead to 'civil war'

John Edwards on mistrial: 'While I do not believe I did anything illegal, I did an awful, awful lot that was wrong'

Romney goes to Solyndra: unannounced visit to controversial energy company

Want more of our best political stories? Visit The Ticket or connect with us on Facebook, follow us on Twitter, or add us on Tumblr. Handy with a camera? Join our Election 2012 Flickr group to submit your photos of the campaign in action.