Republicans have scored victories in two key US elections for governor, a year after Barack Obama was voted in as president.

In Virginia, Republican candidate Bob McDonnell won by a comfortable margin, while another, Chris Christie, ousted the Democrat governor in New Jersey.

In New York, independent Mayor Michael Bloomberg narrowly won a third term over Democrat challenger Bill Thompson.

But Democrats won two Congressional seat races in New York and California.

Correspondents say the gubernatorial defeats are a setback for Mr Obama - who had campaigned for both his party's candidates - as he battles to reform healthcare, pass a climate change bill and rally support for his handling of the war in Afghanistan.

Republicans said the momentum was now behind them ahead of next year's crucial mid-term elections.

While local issues have been paramount in these races, analysts say a win could boost party morale ahead of the 2010 ballots.

Meanwhile in Maine, voters in a referendum rejected a same-sex marriage law passed by state lawmakers earlier this year.

The law was put on hold when conservatives launched a petition to repeal it in a referendum.

In New Jersey, the incumbent Democratic Governor Jon Corzine had fought a bitter campaign against his Republican rival Chris Christie, not only attacking him over his ties to former President George W Bush and his views on abortion and healthcare, but also poking fun at his weight.

With most votes counted, Mr Christie was ahead with about 50% of the vote when Mr Corzine conceded.

He pledged to work with Mr Christie to ensure a smooth transition.

Mr Obama had thrown his weight behind Governor Corzine, repeatedly travelling to New Jersey to back the former Goldman Sachs chief executive on the campaign trail.

'Warning shot'

But Democrats played down Tuesday's gubernatorial defeats.

"These races turned on local and state issues... and despite what some will certainly claim, the results are not predictive of the future or reflective of the national mood," said Democratic Party chairman Tim Kaine.

However, the Republicans said it was a "warning shot" to the White House.

"[Voters] are tired of the spending, tired of the waste and tired of the over-reach they see coming out of Washington," said House deputy leader Eric Cantor.

In Virginia, Democratic party candidate Creigh Deeds phoned Mr McDonnell, a former attorney general, to congratulate him. With most votes counted, the Republican was leading with about 60%.

Only last year President Obama became the first Democratic candidate to carry the state since 1964, although its last two governors have been Democrats.

But independent voters who supported the president in the 2008 election seem to have switched their support to the Republican party candidate in this race.

In other results:

* Democrat Bill Owens won the House of Representatives seat for New York state's 23rd congressional district, defeating Conservative Party candidate Doug Hoffman
* California Lt Gov John Garamendi won a special election to a Northern California congressional seat, keeping the district in Democratic hands
* In New York city, independent Mayor Michael Bloomberg won a closer-than-expected race for a third term. With nearly all votes in, Mr Bloomberg had beaten Democrat Bill Thompson by 51% to 46%
* In Atlanta, councillor Mary Norwood could become the city's first white mayor in a generation if she wins a December run-off against Georgia Senator Kasim Reed, after neither received more than half the votes cast

Mayoral elections were also held in Houston, Boston, Detroit and Pittsburgh.

Tuesday's results are being pored over for clues as to how the two main parties will fare in the 2010 mid-terms.

Next year, the entire House of Representatives, about a third of the Senate and two-thirds of governors will face the vote.


Source: BBC