WASHINGTON — Democrats look like certain underdogs as the political calendar begins on their struggle to maintain their Senate majority in the 2014 elections. The political map — and for that matter, the climate — appears to favor Republicans.
The most vulnerable Democrats are in states that have been GOP-friendly in recent years. The Affordable Care Act, or Obamacare, continues to be politically radioactive in a lot of states. President Barack Obama's approval numbers have been sinking, not to mention that in a presidency's sixth year, the incumbent's party often gets swamped in congressional elections.
Still, Democrats have some reasons for hope. The economy is rebounding. The tea party movement could cause Republicans fits.
And the health care law's impact remains an unknown. Indeed, for all the angst about the law during the 2012 campaign, Obama won re-election and Democrats gained congressional seats.
"There's no question the Affordable Care Act will be an issue," said Nathan Gonzales, the deputy editor of the Rothenberg Political Report, a nonpartisan political analysis. "We can't know how popular or unpopular it's going to be."
Republicans need a net gain of six seats to win control of the Senate. Of the nation's 10 most closely watched races, eight involve seats now held by Democrats, who won them in 2008 as Obama was rolling up a big victory.
"Democrats won in a lot of states typically unfriendly to them," said Kyle Kondik, an analyst at the nonpartisan Center for Politics at the University of Virginia.
But four years later, when Obama ran for re-election, seven of those states flipped and sided with Republican presidential candidate Mitt Romney.
The two Republican seats that might be in play this year, in Kentucky and Georgia, are regarded as Democratic long shots. Both have trended strongly Republican for years.
The Republicans, though, have an internal problem. The party is badly divided between mainstream conservatives talking a gentler, more conciliatory brand of politics and well-financed tea party challengers who are on a crusade to streamline government.
The renegades might force general election favorites in several states - notably Kansas, Mississippi, Kentucky, Texas and South Carolina - to spend precious campaign dollars and time winning the nomination, while running to the right. The risk is that if they survive their primaries, they'll look too extreme for general election voters.
"Tea party contests continue to be a problem for them," said Justin Barasky, a spokesman for the Democratic Senatorial Campaign Committee.
But not like the obstacles that health care and Obama himself present to Democrats, countered Brad Dayspring, senior adviser to the National Republican Senatorial Committee.
"Yes, Obamacare is unpopular, and yes, that will hurt Democrats in 2014," he said. "But their problems are far greater than just Obamacare. Democrats have a credibility crisis."
Republican often cite the botched rollout of the health care law and the revelations of National Security Agency surveillance as wounds that might hurt the Democrats this year.
Here's a look at the key races:
• Arkansas. Democratic Sen. Mark Pryor is regarded as the nation's most vulnerable Democratic incumbent. Democratic former Sen. Blanche Lincoln lost by 21 percentage points in 2010 after Republicans tied her to Obama policies. Romney carried this state two years later with 60.5 percent. Polls show Pryor and Republican Rep. Tom Cotton in a close race.
• Louisiana. Democratic Sen. Mary Landrieu has never had an easy time winning elections in this conservative state and is again considered no shoo-in. Her approval rating had dropped below 50 percent in a recent Southern Media & Opinion Research poll, though she still led potential challenger Republican Rep. Bill Cassidy.
• North Carolina. Democratic Sen. Kay Hagan upset incumbent Republican Elizabeth Dole in 2008, the same time Obama won the state. Times have changed since. Obama lost North Carolina in 2012, one Democratic congressman lost - while another won by a few hundred votes - and voters elected a Republican governor. Hagan also faces questions about her support for Obamacare .
• Montana. Until last month, Montana looked like a safe Republican bet. Democratic Sen. Max Baucus is retiring, and Republican Rep. Steve Daines was the favorite to succeed him. But now Baucus has been tapped as the ambassador to China, and Democratic Gov. Steve Bullock gets to name a successor. Odds are it'll be Lt. Gov. John Walsh, who'd then enter the race as an incumbent.
• Alaska. Democratic Sen. Mark Begich won in 2008 with only 48 percent over incumbent Ted Stevens, who'd just been convicted in a corruption case that later fell apart. This is a tough state to predict. Republicans still have a battle over their nominee, and voters here can be unpredictable and independent.
• Iowa. Democratic Sen. Tom Harkin also is retiring, and Democratic Rep. Bruce Braley wants the seat. There's a lengthy list of potential Republican challengers, and the state party is divided between tea party and establishment types. Braley was running ahead of all the opponents in the latest Quinnipiac poll.
• West Virginia. It's considered one of the likeliest Republican pickups. Republican Rep. Shelley Moore Capito is running strong for the seat of the retiring Democratic incumbent, Sen. Jay Rockefeller, against Secretary of State Natalie Tennant. The health care law plays a big role here.
• South Dakota. Popular former Gov. Mike Rounds is the favorite to get the Republican nomination for the seat of Sen. Tim Johnson, yet another pending Democratic retiree. The biggest Democratic threats, former Rep. Stephanie Herseth Sandlin and Johnson's son, chose not to run. One complication: Republican former Sen. Larry Pressler, who served three terms during the 1980s and '90s, has entered the race as an independent and might draw votes from Rounds.
• Kentucky. Senate Republican leader Mitch McConnell has a dilemma: First, he has to get by tea party favorite Matt Bevin in the primary, meaning he has to stay firmly in the conservative camp.
Democrats are enthusiastic about Secretary of State Alison Lundergan Grimes' chances. To win, McConnell probably has to inch toward the middle. He's won tough races before and remains the favorite in both contests.
• Georgia. Democrats are eyeing the state, where Republicans are embroiled in another nomination fight, for the seat of retiring Republican Sen. Saxby Chambliss.