WASHINGTON (AFP) - The White House Wednesday downplayed election defeats that jolted the incumbent Democrats, denying they were a referendum on the policies of President Barack Obama elected 12 months ago.

A year to the day after Obama vowed before a tumultuous crowd in Chicago that change had come to America, Republicans were trumpeting two victories in key gubernatorial races in New Jersey and Virginia, where they gleefully ousted their Democratic rivals.

It was sweet revenge for Republicans still battered by their drubbing at the polls on November 4, 2008 when Obama was elected America's first black president.

"The Republican Party's overwhelming victory in Virginia is a blow to President Obama and the Democrat Party," Republican National Committee chairman Michael Steele said.

"It sends a clear signal that voters have had enough of the president's liberal agenda."

But White House spokesman Robert Gibbs said Republicans should not presume Tuesday's triumphs will translate into victory in 2010 midterm polls when all the House of Representatives and a third of the Senate is up for election.

"The data from the gubernatorial races demonstrates that voters went to the polls in those two contests and talked about, and worked through very local issues that didn't involve the president," Gibbs said Wednesday.

"If you look at the exit polling, which is pretty clear on this, people went to the polls and voted on local issues not to even register support for or opposition to the president."

Exit polls conducted by television networks backed the White House argument, with 55 percent of Virginia voters and 60 percent of New Jersey voters saying Obama did not factor into their decision.

Obama's favored candidates lost the battle for the governor's mansion to Chris Christie in New Jersey and Bob McDonnell in Virginia even though the president had sought to electrify their campaigns with his star power.

Gibbs said the president had not been watching the returns, and had been "disappointed" Jon Corzine had lost in the heavily Democratic state of New Jersey.

Christie pulled off an upset victory over Corzine with a 49-45 percent margin according to preliminary results, while McDonnell defeated Creigh Deeds by 59-41 percent in Virginia, with almost all precincts reporting.

Virginia helped propel Obama into office a year ago, the first time it had backed a Democratic presidential contender in more than four decades.

But on Tuesday, for the first time in more than a century, a Democrat, Bill Owens, narrowly won a seat in a strong Republican congressional district of upstate New York.

Owens narrowly defeated conservative Republican challenger Doug Hoffman, who pulled back from behind after being endorsed by the others on the conservative right including former would-be vice president Sarah Palin, which caused a more moderate Republican candidate to drop out.

"That district sent its first non-Republican to Congress since before the Civil War. So, I think it proves that anger can get you 45 percent of the vote," Gibbs said, adding it does not mean you can win the election.

The results would not impact the president's agenda as he tries to lead the United States out of recession, Gibbs added.

"I think voters are concerned about the economy, I don't think the president needed an election or an exit poll to come to that conclusion," he said.

"The president will continue to spend his time focused on the issue that is most on the minds of the American people and that's the economy."

Gibbs also highlighted that in 2001 when former president George W. Bush enjoyed an 80 percent popularity rating after the September 11 attacks, Democrats had won the governor's mansion in Virginia and in New Jersey.

In other elections, New York Mayor Michael Bloomberg was re-elected to a third term in a surprisingly close contest after he poured millions of his own money into the campaign and changed the rules so he could stand again.

And in Maine, voters soundly rejected a law to allow same-sex marriage, in a blow to gay rights advocates hoping the northeastern US state would become the first in the country where voters directly approve gay unions.