HOUSTON — Bill White, the popular Democratic mayor of Houston, said Friday that he would run for governor of Texas, changing the dynamic in a heated contest and giving Democrats a faint hope for the first time in 15 years that they might be able to take back the governor’s office.
Mr. White, 55, who is leaving office in January, had been running for Ms. Hutchison’s Senate seat, but he switched his goals after heavy lobbying from Democratic leaders across the state, who were facing the 2010 election with a sense of futility.
As conservative Democrats defected to the Republicans, Mr. Bush and his party swept the state four years later and the Republicans have dominated Texas ever since.
Governor Perry, a staunch conservative, took over from Mr. Bush in 2000 and has won twice since then, becoming the longest-serving governor in the state’s history. He is pushing for an unprecedented third four-year term.
The critical moment for Democrats came last week when the strongest of the four Democrats vying for the nomination, Tom Schieffer of Fort Worth, met with Mr. White and said he would throw his support behind the mayor if he chose to run.
In announcing his candidacy, Mr. White, who served as deputy energy secretary under President Bill Clinton, came out swinging against Governor Perry, accusing him of failing to improve the state’s high schools and of turning state commissions into patronage mills for his campaign donors. He also took a swipe at the governor for expressing sympathy with secessionists.
“Shouldn’t we be the state that leads the nation, not that leaves the nation?” Mr. White said.
Mark Miner, a spokesman for the governor, responded, “Governor Perry is focused on running the state and his race, not what the Democrats are doing.”
Until now, Governor Perry’s main competition came from Senator Hutchison, who hopes to wrest the nomination from him in a March primary.
The Democrats, meantime, had fielded a weak lineup of candidates. Among them were the humorist and singer Kinky Friedman and a hair-products magnate, Farouk Shami of Houston, who is a political neophyte.
The strongest candidate was Mr. Schieffer, but he failed to ignite much interest outside of Austin.
Political strategists say Mr. White has a better chance of success but still faces an uphill battle in a state where big-city mayors have failed to win on a statewide level and where Republicans have enjoyed a six- to nine-point advantage in recent elections.
Mr. White has $6.5 million in his campaign fund, including about $1 million of his own money.
His candidacy has generated excitement among Democrats in large part because Mr. Schieffer was gaining so little traction, political scientists said.
“Some of this exuberance is fueled by an overwhelming sense of relief,” said Jim Henson, director of the Texas Politics Project at the University of Texas. “Democratic activists and fund-raisers now have the opportunity to change their bet from what was looking like a very poor wager.”
The state’s Republican Party has put out an Internet ad claiming Mr. White is “too liberal for Texas,” and Republicans have criticized him as being too reluctant to crack down on illegal immigrants and too willing to support limits on carbon emissions.
Mr. White has labored as mayor to build a reputation as a nonpartisan executive with a businesslike way of tackling tough problems.
He has cut taxes in Houston and won praise for reducing smog and steering the city through Hurricanes Katrina and Ike. He won re-election twice by large margins and would probably be re-elected were it not for term limits.
“I know I don’t have the polish or the fame of the career politicians,” he said, having had a long career in politics. “But I know how to get things done. I know and you know the difference between rhetoric and results.”