NEW YORK (Reuters) - Republican Mitt Romney has drawn almost even with President Barack Obama in a new poll asking U.S. voters who they would support if the two men ran against each other in the 2012 U.S. presidential election.

The McClatchy-Marist poll released Wednesday showed Obama with the support of 46 percent of 1,084 registered voters surveyed, compared to 45 percent for Romney, in a hypothetical match-up between the Democratic president and the Republican who is exploring a possible presidential run.

Nine percent of respondents said they were undecided. In a January poll, Obama led Romney 51 percent to 38 percent.

Romney, the former governor of Massachusetts, this month formed an exploratory committee to raise money for a challenge to Obama in the 2012 election.

The poll offered more sobering news for Obama. Forty-four percent of the registered voters questioned said they definitely plan to vote against Obama in 2012, while 37 percent said they definitely plan to vote for him and 18 percent were unsure.

Obama, who has announced plans to seek re-election, holds bigger leads over other possible Republican challengers than against Romney, according to the McClatchy-Marist poll.

Obama led former Arkansas Governor Mike Huckabee 48 percent to 43 percent with 9 percent undecided. Huckabee has said he will wait until summer to make a decision on whether to seek the Republican nomination to face Obama.

Pitted against former Alaska Governor Sarah Palin, Obama led 56 percent to 34 percent with 10 percent undecided.

Obama held a similar lead against real estate tycoon Donald Trump -- 54 percent to 38 percent with 8 percent undecided. Trump has been flirting with a 2012 presidential run.

Romney led the potential Republican field when poll respondents who described themselves as Republicans or Republican-leaning independents were asked who they would vote for if the party's presidential primary was held today. Romney drew the support of 18 percent, followed by Huckabee with 17 percent and Trump with 13 percent.

"If there is a silver lining for his (Obama's) re-election, it's the lack of clarity in the GOP field,'' said Lee Miringoff, director of the Marist College Institute for Public Opinion, referring to the potential Republican candidates.

The poll had a margin of error of plus or minus 3 percentage points.

(Editing by Will Dunham)

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