The Senate majority leader is trailing two GOP candidates in next year's race in Nevada.
Danny Tarkanian, a former University of Nevada-Las Vegas basketball player and son of a legendary basketball coach, leads Reid 50 to 43 percent in a hypothetical head-to-head.
Sue Lowden, former chairwoman of the Nevada Republican Party who officially launched her campaign Thursday, is leading Reid 50 to 40 percent, according to a recent poll by Rasmussen Reports.
But many political analysts believe Reid will prevail because of his opponents' lack of prominence.
The Connecticut senator, chairman of the Banking Committee and perhaps the most vulnerable Senate Democrat in 2010, is facing the toughest re-election fight of his nearly 30 years in Congress.
Polls show him trailing former GOP congressman Rob Simmons, and he's also facing competition from Linda McMahon, wife of WWE executive Vince McMahon.
Dodd's popularity has tumbled in the wake of the financial meltdown and his failed 2008 presidential bid. He provoked a home-state backlash after temporarily moving his family to Iowa before his poor showing in the caucuses there.
Dodd has been criticized for collecting Wall Street contributions while chairing the Senate banking panel. He's also come under fire for his role in writing a bill that protected bonuses for executives at bailed-out insurer American International Group Inc. and for allegations he got favorable treatment on two mortgages with Countrywide Financial Corp.
The Pennsylvania Democrat, chairman of the House Defense Appropriations Subcommittee, has been dogged by a federal corruption investigation into his ties to a Washington lobbying firm. And he has drawn national attention for being critical of his own constituents, once even suggesting that many of them are racist.
He is facing a well-heeled opponent, the third time since his criticism of the Iraq War gave Republicans ammunition.
The Missouri congressman, chairman of the House Armed Services Committee, is facing challenges from five Republicans in his first competitive race since being elected in 1976.
His rural district favored John McCain in last year's presidential election by 60 percent.
Obey, a longtime Wisconsin congressman, is chairman of the influential House Appropriations Committee and is considered the architect of the stimulus package that is at the center of a fierce partisan battle over the current economic recovery.
He faces tough GOP opposition from a local district attorney, Sean Duffy, who is a former star of MTV's reality series "The Real World."
Duffy told the Washington Independent that he'd raised $140,000 for the third quarter, more than half as much as Obey's challenger raised for the entire 2008 election cycle.
The California senator, who has taken heat in recent months for clashes at Senate hearings, is facing a potentially tough election challenge from prominent businesswoman Carly Fiorina, who is within striking distance in a recent poll.
A Rasmussen Reports poll in the summer showed that Fiorina is trailing by only 4 percentage points in a hypothetical head-to-head with the three-term incumbent. The poll put Boxer's support in such a face-off at only 45 percent, with 7 percent of survey respondents saying they're undecided.
Lincoln took control of the agriculture committee after Sen. Tom Harkin was tapped to lead the health committee following Sen. Ted Kennedy's death.
Lincoln, a moderate Democrat from Arkansas, is a staunch supporter of government farm subsidies, yet she faces a tough re-election in a decidedly conservative state that President Obama lost by 20 percentage points last year.
Her prospective Republican opponent, state Sen. Gilbert Baker, already has raised hundreds of thousands of dollars for his campaign.
While the midterm elections are still more than a year away, Republicans are beginning to lick their chops as rising unemployment rates, a record federal deficit and President Obama's slipping support signal possible double-digit losses for Democrats in the House and key defeats in the Senate. The GOP is aiming high, hoping to knock off some Democratic leaders, in addition to lawmakers with less seniority. The races are still wide open, and incumbents traditionally are tough to beat. Here's a look at seven of the biggest Democrats facing the biggest threats in the upcoming elections. READ MORE >>