"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.
