hclinton_fc.jpgWASHINGTON (AP) _ Add this to the divisive debate over race in the U.S. presidential campaign: Whites who said race was important in picking their candidate have been about twice as likely to back Sen. Hillary Rodham Clinton as Sen. Barack Obama.

Exit polls of voters in Democratic primaries also show that whites who considered the contender's race _ Clinton is white, Obama is black _ were three times more likely to say they would only be satisfied with Clinton as the nominee than if Obama were chosen.

The figures shed some light on race's effect on a competition that moves to the April 22 primary in Pennsylvania, which has a slightly greater proportion of whites than the U.S. average. The numbers also underscore the challenge Obama could face in the general election, when whites will comprise a larger share of voters and tend to be more conservative than those participating in the Democratic primaries.

Throughout the campaign, Obama has tried to avoid being cast narrowly as a black candidate. Last Friday, he was the only one of the three major presidential contenders to not travel to Memphis, Tennessee, to mark the 40th anniversary of the assassination of the Rev. Martin Luther King, Jr.

“The only thing Obama can do is keep the campaign about change in the future'' while running as “a candidate for the whole country,'' said David Beattie, a Democratic pollster.

Whites who said race influenced their decision were outnumbered more than six to one by those saying it was insignificant. Whites who say they discounted race also leaned toward Clinton, though by more modest margins.

Obama has trailed Clinton, the New York senator, among whites nationally yet won the white vote in six state primaries. He leads overwhelmingly with blacks.

In the exit polls, whites saying they considered the candidate's race were likelier to be from the South and rural areas, less educated, lower earning and older. That is consistent with voting so far, in which Obama has done better among whites with more education and higher incomes, especially men.

Ohio _ which has similar proportions of downscale whites to Pennsylvania _ was among the states with higher numbers of whites saying race mattered. Clinton won Ohio's March 4 primary by 10 percentage points. A recent Quinnipiac University poll showed Clinton with a solid lead in Pennsylvania among whites, while Obama led easily with blacks.

Pollsters have long expressed doubts about using polls to precisely gauge voters' feelings about the sensitive issue of race, concerned that some people give answers they think are socially acceptable.

The phenomenon even has a name, the Bradley effect, after Tom Bradley's losing 1982 run for California governor despite favorable polls, making him one of several prominent black candidates in the 1980s who did worse than surveys suggested. Critics argue that other factors could account for the discrepancies and say white voters' reluctance to support black candidates has diminished since then.

No one doubts some voters are influenced by a candidate's race. The pivotal questions this year are how many are abandoning Obama because he is black, and whether they are offset by others supporting him for racial reasons. Many of this year's primaries have already seen increased turnout among black and younger voters.

“We'd be foolish to say it's not a factor,'' Harvey Gantt, an Obama supporter who lost two senatorial races against Republican Jesse Helms in North Carolina in the 1990s, said of race.

But Gantt, who was the first black mayor of Charlotte, North Carolina, said he believes those voting for racial reasons can be offset by higher turnout among blacks and others eager to support a black candidate. He and others said fewer voters are letting a candidate's race outweigh their concerns about issues or political preferences.

So far, the outlook for November is unclear. A poll last month by the nonpartisan Pew Research Center showed Clinton and Obama both trailing likely Republican nominee John McCain among whites by under 10 percentage points, but some expect Obama's race to be telling.

“You ain't heard nothing at all yet if Obama is the nominee and it's Obama-McCain,'' said Democratic Rep. Alcee Hastings, a member of the Congressional Black Caucus.

Cornell Belcher, an Obama pollster, argued that the candidate has done well with whites in some states and will attract more as the campaign continues.

The exit polls also reveal a tilt toward Clinton, who would be the first female president, by those who strongly considered the candidate's gender. While those saying sex was not a factor leaned slightly toward Obama, six in 10 of those saying gender was important have supported Clinton, including more men. Most said the candidate's gender was not important.

Whites who said race was their top consideration or an important factor preferred Clinton over Obama by 63 percent to 32 percent. Those who said race was not consequential backed Clinton by a narrower 11 percentage points.

Nearly one in three blacks said race was significant in choosing their candidate. Eighty-eight percent of blacks who said race was an important factor voted for Obama, compared to 81 percent of those who said they did not consider race.

At the same time, 41 percent of whites who said race was important said they would only be satisfied if Clinton were the nominee, compared to 14 percent who said they would only be happy with Obama. Another 36 percent said either would be fine.

Whites who said race was not a factor were nearly evenly divided when asked which candidate would satisfy them.

The data is from exit polls in Democratic primaries conducted for The Associated Press and television networks in Alabama, Arkansas, Arizona, California, Connecticut, Delaware, Georgia, Illinois, Louisiana, Massachusetts, Missouri, Mississippi, New Jersey, New Mexico, New York, Ohio, Oklahoma, Rhode Island, Tennessee, Texas, Utah and Vermont.

In these states, 24,657 voters were asked how strongly they considered race, including 16,764 whites and 5,366 blacks. The margin of sampling error was plus or minus 1 percentage point for all people and whites, 2 points for blacks.