* McDonnell wins easily in Virginia
* Christie defeats incumbent Corzine in New Jersey
* Democrat wins New York congressional district (Updates with more analysis, details)
By Steve Holland
WASHINGTON, Nov 3 (Reuters) - Republicans rolled to victory in Virginia and New Jersey governor's races on Tuesday in a sharp blow to Democrats that showed the limits of U.S. President Barack Obama's political clout.
After suffering a one-two punch in those two states, Democrats salvaged a victory over a conservative candidate in a congressional district in upstate New York in a race that exposed a split in the Republican Party.
Republican Bob McDonnell scored an easy victory over Democrat Creigh Deeds in Virginia. In New Jersey, Republican Chris Christie had a tougher time with incumbent Democratic Governor Jon Corzine but prevailed.
The victories buoyed Republican hopes that they had emerged from the political wilderness after losing control of the U.S. Congress in 2006 and the White House in 2008.
And it raised questions for Democrats as they try to protect strong majorities in the U.S. House of Representatives and the Senate in 2010, amid concerns about the weak U.S. economy and their inability so far to reduce the country's unemployment rate, now at 9.8 percent.
"Losing Virginia in a landslide, his key swing state victory in 2008, plus the loss of New Jersey means a bad night for Obama," said Larry Sabato, a University of Virginia political scientist. "Presidents have to take their lumps and Obama has just taken a big one."
The Virginia and New Jersey losses suggested Democrats have a challenge in trying to attract voters to the polls without Obama's name on the ticket. Democratic turnout suffered particularly in Virginia.
Some analysts wondered aloud whether some moderate Democratic members of Congress might look at the results and question whether expensive programs such as a broad overhaul of the U.S. healthcare system are politically palatable.
"It could have an effect that people in Congress say 'you know I'm not going to go along with some of Obama's stuff, I'm really scared, we've gotta be careful, we're going into 2010,'" said Democratic consultant James Carville on CNN.
A year ago, Obama became the first Democratic presidential nominee to win Virginia since 1964. Obama campaigned twice for Deeds but Democrats were unable to muster a large turnout the way they did a year ago despite holding the state for the last eight years.
Republicans had not won a statewide race in New Jersey since 1997. Obama won the state by 16 percentage points and traveled there to campaign three times for Corzine, a former Wall Street executive who pumped $23 million of his own money into the campaign.
OBAMA NOT WATCHING RESULTS
The president was described by the White House as not having watched the election returns, and spokesman Robert Gibbs earlier dismissed the potential impact of the governors' races on Democrats and the 2010 elections.
"These races turned on local and state issues and circumstances and on the candidates in each race -- and despite what some will certainly claim -- the results are not predictive of the future or reflective of the national mood or political environment," said Democratic Party chief Tim Kaine.
But the Republican Party was eager to blame the policies of Obama and the Democrats.
"Tonight voters sent a warning shot to Democrats and the White House: they are tired of the spending, tired of the waste and tired of the over-reach they see coming out of Washington," said Eric Cantor, the No. 2 Republican in the U.S. House.
ABC News said majorities of voters in both Virginia and New Jersey approved of Obama's handling of his job -- 51 percent in Virginia and 57 percent in New Jersey.
But it said 90 percent in New Jersey and 85 percent in Virginia said they were worried about the direction of the country's economy in the next year.
Democratic strategist Bud Jackson said the long night for Democrats could be seen as an indication of impatience with Obama.
"A lot of these people who voted for Obama last year, they voted for the hope. Well, hope hasn't had time to meet reality so there are a lot of independent voters who aren't completely sold on Obama yet and they won't be until they start seeing some results," he said.
DEMOCRAT WINS IN NEW YORK
U.S. television projected Democrat Bill Owens defeated Conservative Party candidate Doug Hoffman in upstate New York's 23rd congressional district.
The House seat had been left vacant when Obama picked Republican John McHugh as his Army secretary. The race took a bizarre twist over the weekend when Republican candidate Dede Scozzafava withdrew because of flagging support and endorsed the Democrat.
Democrats charged the race was an example of divisions within the Republican Party between conservatives and moderates. Hoffman had been endorsed by conservative Republicans such as Sarah Palin, last year's Republican vice presidential nominee.
New York Mayor Michael Bloomberg, who engineered a rules change to allow him to run for a third term, was re-elected. The billionaire mayor defeated Democrat Bill Thompson by a narrower margin than expected after spending almost $90 million on the campaign to Thompson's $7 million.
In Maine, a "citizen's veto" is on the ballot to overturn a May 2009 law allowing same-sex marriage. If the law is upheld, Maine would become the sixth U.S. state to allow gay marriage, but the first to approve such a law at the ballot box -- a potential turning point for gay rights after a stinging 2008 defeat in California. (Additional reporting by Tabassum Zakaria and JoAnne Allen in Washington and Ros Krasny in Boston; editing by Anthony Boadle)