SEATTLE - Seattle Mayor Greg Nickels conceded defeat Friday in his bid for a third term, failing to advance past the primary after getting battered for his bungling of December snowstorms that paralyzed the city.

The concession marks a surprising development for a politician viewed as a national leader on environmental issues and so respected by his peers that he was chosen last spring to head the U.S. Conference of Mayors.

Nickels said at a City Hall news conference that he called to congratulate the two challengers who topped him in Tuesday's primary - T-Mobile executive Joe Mallahan and Sierra Club activist Mike McGinn, who advance to November's general election. The race is technically nonpartisan, but all three of the top candidates are Democrats.

"The people of Seattle have decided it's time for a new generation of leadership," Nickels said.

In a speech that was gracious and often self-deprecating, he touted his record, including the recent opening of a new light rail system, and said he had always wanted to be a mayor who made tough decisions even if it made him unpopular.

"I have succeeded beyond my wildest dreams," he joked.

The most recent tally by elections officials had Nickels receiving just 25.6 percent of the vote - 1,170 votes out of second place - to Mallahan's 27.2 percent and McGinn's 26.7.

About 30,000 ballots still need counting. But Nickels said he wanted to step aside to allow voters to focus on the other two candidates - both political newcomers - rather than drag out a recount.

On environmental issues, Nickels helped persuade nearly 1,000 mayors around the country to abide by the standards of the Kyoto Protocol on global warming.

But more prosaic issues made him less popular at home, including the Seattle SuperSonics' move to Oklahoma City, the city's response to the series of December snowstorms and his support for a multibillion-dollar downtown tunnel, which would replace a crumbling elevated highway along the city's waterfront.

Nickels said he hasn't decided whom he'll support in the November election, or what his next career move will be.

He has spent his entire adult life in government, serving as a city council aide before being elected a King County councilman and then Seattle mayor. He said he hoped to continue to serve the public in some fashion.