WASHINGTON -- Mississippi, one of the nation's most conservative states, has not elected a Democratic senator in a quarter-century. It has voted for Republican presidential candidates in the last seven elections.
But this year, there is a real chance that the state will send a Democrat to the Senate.
The outlook for the GOP is so grim that party leaders have readily conceded there is no chance they can regain control of the Senate in 2008, even though Democrats' current majority is slim, 51-49.
"If you have an R in front of your name, you better run scared," said Sen. John Ensign (R-Nev.), chairman of the National Republican Senatorial Committee, who says the party will do well if it holds its losses to three or four seats.
The Mississippi race between Democratic former Gov. Ronnie Musgrove and Republican Sen. Roger Wicker distills the wide range of factors that have put congressional Republicans in their weakest position since the Watergate scandal of the 1970s.
The overall political climate, shaped by the sluggish economy and President Bush's low approval ratings, is souring many voters on Republicans. The party has been hobbled by a stampede of retirements by senior Republicans, including Mississippi Sen. Trent Lott. After Lott quit in 2007, Wicker was appointed to replace him.
Barack Obama's presidential campaign has generated a big boost in Democratic voter registration, especially among African Americans, who make up more than a third of Mississippi's population. Other quirks, such as ethics scandals, are putting more Republican Senate seats at risk than seemed likely a year ago.
In June 2007, the nonpartisan Cook Political Report identified only one race for a Republican Senate seat as a real tossup. Now it identifies seven Republican seats as at risk.
The stakes for Obama in the Senate races are high. If he is elected president, the biggest obstacle to his goals could be in the Senate, where parliamentary rules mean that it can take 60 votes to approve legislation. The Senate currently includes 49 Democrats and two independents who are aligned with the Democratic caucus.
"Big changes don't happen without big Senate majorities," Obama wrote in a recent letter urging Democrats to contribute to Senate campaign coffers.
For now, most political analysts are predicting a Democratic gain of four to eight seats, which would leave the party short of the 60-vote threshold. But Republicans are worried, because bigger gains are not out of the question: Democratic fundraising is strong and the battlefield is heavily tilted against the GOP.
"This is the toughest election in my 32 years in the United States Senate," wrote Sen. Orrin G. Hatch (R- Utah), vice chairman of the National Republican Senatorial Committee, in a fundraising letter.
Senate Republicans are defending 23 seats; 12 Democratic seats are at stake. No Democrats are retiring -- a good thing for the party, because it is usually easier to reelect an incumbent than to win an open seat.
By contrast, three senior Republicans are quitting, including two who probably would have easily won reelection. The retirements of Sens. John W. Warner of Virginia and Pete V. Domenici of New Mexico open the way for likely Democratic takeovers by former Gov. Mark Warner in Virginia and Rep. Tom Udall in New Mexico.
In Colorado, the retirement of GOP Sen. Wayne Allard has led to a close race between two House members.
Sen. Charles E. Schumer (D-N.Y.), chairman of the Democrats' Senate election committee, said that a year ago he expected four Democratic incumbents to have a fight on their hands. But only one, Sen. Mary L. Landrieu of Louisiana, has drawn serious opposition.
Mississippi has emerged as an unexpected battleground largely because Lott, a powerful and well-established Republican, quit the Senate to become a lobbyist. Wicker, who had been a House member, was appointed to replace him, but he has not established himself firmly enough statewide to assure easy reelection.
Musgrove, his Democratic opponent, is a well-known former governor and is expected to benefit from the Obama campaign's efforts to register new voters, including African Americans.
Obama's nationwide registration drive also could help Kay Hagan, the North Carolina Democrat who is challenging GOP Sen. Elizabeth Dole. Obama inspired a big increase in black voter turnout during the state's primary.
Though Democrats may benefit from the turnout generated by Obama, Schumer says that the party's candidates in conservative states will probably keep their distance from the national ticket.
"We have been running a campaign that is Mississippi first," said Adam Bozzi, Musgrove's communications director. "We have to run a campaign based on Ronnie Musgrove and Roger Wicker."
But in other states, Democratic Senate candidates have embraced Obama.
In Oregon, Democratic candidate Jeff Merkley's campaign shares office space with the Obama staff. Obama's name appears with Merkley's on campaign fliers. Obama is so popular in Oregon that the Republican incumbent, Sen. Gordon H. Smith, has run an ad bragging about his record of working with Obama.
Another improbable battleground is Alaska, which has not elected a Democratic member of Congress since 1974, and which gave Bush 61% of its vote in the last presidential election. This year, GOP Sen. Ted Stevens is facing a tough reelection fight, shadowed by ethics questions concerning his ties to an oil field services contractor.
Democrat Mark Begich, the mayor of Anchorage, is leading in some polls. He also is expecting to benefit from a surge of Democratic activism organized by Obama, who won the state's caucuses by a landslide.
While the Senate races are roiling some states unexpectedly, two incumbents whom Democrats considered top targets are holding their own.
Sen. Susan Collins (R- Maine) is out-polling her Democratic rival, Rep. Tom Allen. And Sen. Norm Coleman (R-Minn.), while still in a tough race, is benefiting from missteps and controversies surrounding Al Franken, the comedian running against him.