Republican Chris Christie, left, holds hands with his daughter, Bridget, after he and his running mate, Kim Guadagno, right, unseated the incumbent...

(AP Photo/Henny Ray Abrams)

Republican Chris Christie, left, holds hands with his daughter, Bridget, after he and his running mate, Kim Guadagno, right, unseated the incumbent Democratic Gov. Jon Corzine, Tuesday, Nov. 3, 2009 in Parsippany, New Jersey.

NEW YORK— Voters nervous about the economy and fed up with the political establishment dominated the off-year elections, sending a strong message to President Barack Obama, who won the White House as a change agent but has himself become the face of political power and incumbency.

Independents who supported Obama broke heavily for Republicans Tuesday, helping the GOP win marquee governors' races in Virginia and New Jersey. And the coalition of younger, minority voters who powered Obama's victory last year was replaced by an electorate that was noticeably whiter, especially in Virginia, where Democrat Creigh Deeds lost in a landslide.

Yet Democrats weren't the only ones in danger, as voters also vented their frustration at incumbents and party insiders.

In upstate New York, Democrat Bill Owens won a House seat held for decades by Republicans in a special election dominated by a fierce intraparty GOP split.

There, conservatives and national Republican figures led by former vice presidential candidate Sarah Palin helped force out assemblywoman Dede Scozzafava, the Republican candidate chosen by GOP county chairmen, in favor of Conservative Party candidate Doug Hoffman. The conservatives were incensed by Scozzafava's support for abortion rights and gay marriage.

In New York City, independent Mayor Michael Bloomberg barely won a third term against a little known, poorly funded Democratic challenger. Polls going into the election showed voters generally approved of Bloomberg's job performance but resented his aggressive effort to get the city's term limits law lifted and his expenditure of as much as $100 million of his own money to stay in power.

To be sure, each race was as much about local issues as about firing warning shots at the politically powerful. But taken together, the results of the 2009 off-year elections could imperil Obama's ambitious legislative agenda and point to a challenging environment in midterm elections next year.

"In bad economic times, people don't like the politicians who are holding the reins of power," said Jack Pitney, a political science professor at Claremont McKenna College in California. "For Obama, it means the 2008 election was not a key to everlasting success. It was the first step in an ongoing journey, and he's going to have to work very hard to continue earning voters' trust."

For now, Obama must worry about the impact of the 2009 contests on health care reform, his signature legislative priority.

Earlier Tuesday, Senate Majority Leader Harry Reid said a vote on health care may not happen before the end of the year _ a sign that some Democrats don't feel confident tying themselves to Obama and casting a controversial vote for his reform effort.