"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.