Democratic Sen. Mary Landrieu overcame a determined GOP challenge led by President Bush and won a second term Saturday, defeating Republican Suzanne Haik Terrell, the state elections commissioner.
With 98 of precincts reporting, Landrieu had 624,214 votes, or 52 percent, and Terrell had 587,423, or 48 percent.
The victory gives Landrieu's party a midterm consolation prize that limits the GOP's Senate majority to 51 seats.
The GOP also surrendered a U.S. House seat in the final election of the calendar year. Republican Lee Fletcher lost to Democratic state legislator Rodney Alexander by just 518 votes in the race for the seat Republican John Cooksey gave up to make an unsuccessful Senate bid.
With all precincts reporting, Alexander had 85,720 votes and Fletcher had 85,202 votes. Fletcher did not immediately say whether he would request a recount.
Bush had campaigned here last week in hopes of ensuring a victory for Terrell, who promoted herself as a close friend and ally of the president. In response, Landrieu characterized herself as a centrist who backed Bush three-fourths of the time but wouldn't be a "rubber stamp" for the White House.
Secretary of State Fox McKeithen said he expected turnout to be 45 percent -- low by Louisiana standards. Voters seemed dismayed by the sharp salvos between the two New Orleans women who share the same views on most political issues.
Tom Loesch, a Democrat from New Orleans, said he was "saddened to have to choose between two Republicans, one of them in a Democrat's clothing." He said he had to support Landrieu because he "didn't want to give Bush anything else."
Terrell, 48, emerged from obscurity three years ago to become the first Republican woman to win statewide office, as elections commissioner. She was trying to become the first Republican senator here since Reconstruction.
Landrieu, 46, has been in politics all her life. The daughter of former New Orleans Mayor Moon Landrieu, she won her first term six years ago by only 6,000-votes, prompting her to joke that she was no "Landslide Landrieu."
Landrieu tried to maintain her centrist image this time around, relying on fellow Democratic Sen. John Breaux but no party big-hitters like former President Clinton. Her opponent raised more money than she did late in the campaign.
While the rest of the nation decided its congressional elections Nov. 5, Louisiana held a unique open primary where candidates from both sides run. Landrieu failed to get the simple majority needed for outright victory and wound up in the runoff with second-place finisher Terrell.
Republicans held 51 seats in the Senate after the November elections and took aim at this race for the icing on the cake. Another GOP seat would have been ammunition in the fight to get more committee seats, and would have provided a cushion in case a Republican senator left office and was replaced by a Democrat.
Landrieu was caught in a bind during the campaign, since Bush carried the state in 2000. Her primary campaign ads boasted that she had voted with the president 74 percent of the time but not on issues that were harmful to Louisiana.
That strategy prompted black leaders complained that Landrieu sounded like a Republican, and kept black voters at home in large numbers on primary day. For the runoff, Landrieu fired her strategists and launched a more aggressive attack in a bid to appear more independent.
Terrell's message changed from a primary campaign that said the president needed control of the Senate to one that stressed that Louisiana "has one good senator but needs one in the majority party to get more done for the state." It was a reference to Breaux, who is as popular in Louisiana as the president -- Bush even praised Breaux campaigning for Terrell.
Loyalty to Bush became a major issue, with both candidates not far apart on issues such as Social Security, Medicare, prescription drugs for the elderly and homeland defense. Both support Bush's stand on Iraq.
The glaring difference between the two Roman Catholics was abortion: Landrieu supports abortion rights and Terrell is anti-abortion.
In the House race, Fletcher, 36, and Alexander, 55, spent weeks swapping bitter accusations and attack ads. Both touted themselves as conservative businessmen best suited to take the seat Cooksey held for three terms.
Fletcher is the congressman's former chief of staff.
The Associated Press contributed to this report.