NEW ORLEANS – Mayor Ray Nagin turned back a re-election challenge from Louisiana’s lieutenant governor, Mitch Landrieu, and will be sworn in for a second term on May 31, the day before the hurricane season begins.

With all the votes tallied from Saturday’s runoff election, including almost 25,000 absentee ballots, Mr. Nagin had 52% of the 113,591 votes cast, to 48% for Mr. Landrieu.

Mr. Nagin, 45, will have four more years to guide the rebuilding of a city that nine months ago was 80% submerged by Hurricane Katrina’s floodwaters, and to which less than half the pre-storm population of 485,000 has returned.

“This city is positioned for growth,” Mr. Nagin said in his victory speech to supporters gathered at the New Orleans Marriott hotel on Saturday night just after 10:30 p.m. local time. “This great city of New Orleans is ready to take off.”

In winning re-election, Mr. Nagin overcame criticism of the pace of recovery and his frequent policy shifts, as well as a tendency to make statements for which he later had to apologize.

One was his pronouncement that New Orleans would remain a “chocolate city,” meaning majority black; he also said last year’s hurricanes showed “God is mad at America.”

In his acceptance speech, Mr. Nagin made light of his misadventures with off-the-cuff comments. “I’m out of energy, ladies and gentlemen, so you’re not going to get the typical Ray Nagin speech,” he said, provoking laughter from the crowd. “I’m not going to get in trouble tonight.”

Mr. Nagin’s task is formidable. Large sections of the city remain in ruins and mostly devoid of residents as homeowners and landlords await a comprehensive recovery plan and federal housing money. Displaced voters who cast absentee ballots and traveled to satellite polling stations elsewhere in Louisiana were almost evenly divided between the candidates.

Mr. Landrieu, in his concession speech, reprised one of his central campaign themes, one that Mr. Nagin also used repeatedly in his address, calling for unity in a city often divided by race and class. “We, come hell or high water, and we have had both, are going to find higher common ground and find a way together to rebuild this great city,” he said.

Mr. Nagin in turn praised Mr. Landrieu and the campaign he ran and pledged to work with everyone from Governor Blanco to the city council, with which he has clashed.

Mr. Nagin also thanked President Bush, whom he harshly criticized immediately after Katrina, for providing federal money. The mayor said he and Mr. Bush shared the distinction of being “probably been the most vilified politicians in the country.”

The president, who suffered a slide in public opinion polls after the hurricane, called Mr. Nagin yesterday to congratulate him. “They discussed the importance of the federal and city governments continuing to work closely to rebuild New Orleans,” an administration spokeswoman, Christie Parell, said of the midday telephone conversation.

Mr. Landrieu, 49, is the son of New Orleans’s last white mayor, Moon Landrieu, who served until 1978, and the brother of Senator Landrieu. A veteran of 16 years in the state Legislature and a member of Ms. Blanco’s administration, he said he had the political skills to run the recovery more effectively.

Many Nagin supporters such as Joseph Robinson, 22, an electrician from the middle-class, largely black Gentilly section, said they didn’t want to change leaders at a time when extraordinary challenges face the city.

“Nagin’s been through the problems already,” Mr. Robinson said. “He has more experience and can do what we need.”

Mr. Nagin ran Cox Communications’s local cable company before turning to politics four years ago. In his first election as mayor, Mr. Nagin received virtually all the white vote and less than half the black vote in beating then police chief Richard Pennington, who also is black.

This time, Mr. Nagin lost most of his support among whites and was returned to office on the strength of black support, the returns showed.