LOUISVILLE, Kentucky (CNN) -- Tuesday may end up a big night for Barack Obama, giving him a majority of all possible pledged delegates in the Democratic race for the White House. But exit polling in Kentucky -- where CNN is projecting rival Sen. Hillary Clinton will win by a wide margin -- suggests that he still has big problems in states with a large majority of older, white and blue-collar voters.
Nearly half of Democratic voters in Kentucky polled Tuesday said they would either vote for Republican Sen. John McCain or not vote at all in November if Obama is the Democratic nominee. Among 1,278 people polled, 33 percent said they would pick McCain over Obama, and 16 percent said they would not vote at all.
By comparison, 76 percent said they would choose Clinton over McCain, with only 17 percent supporting the Republican and 6 percent not voting.
It's the second time in as many weeks that the Illinois senator has seen such troubling numbers. In last week's West Virginia primary, exit polls showed 27 percent of voters saying they'd choose McCain over Obama and 17 percent saying they wouldn't vote.
Like West Virginia, Kentucky is largely blue-collar, white and rural, with a large percentage of older voters. Each of those demographics has consistently chosen Clinton over Obama in this year's primary campaign.
Eighty-nine percent of the Kentucky voters polled Tuesday were white, 63 percent were 45 or older, and 66 percent did not have a college degree.
And many flatly stated that, as Obama seeks to become the first black candidate to win a major U.S. party's nomination, race played a role in their decision.
Twenty-one percent of all respondents and 19 percent of whites said race was a factor, and 7 percent of all voters said it was the most important factor.
Obama supporters are downplaying the perceived rift. They say that many voters who are strongly supportive of Clinton will come back into the fold by November and that Obama is stronger in states like Kentucky and West Virginia than he has appeared.
"There may be something to keep an eye on there for the general election," said Obama supporter and CNN contributor Jamal Simmons. "He did not campaign very hard in West Virginia. He's not campaigning very hard in Kentucky.
"What we've seen is that when he starts to spend time in states, those numbers move, and he starts to close on Sen. Clinton."
Clinton also sought to tamp down the divisions as she spoke to a crowd of cheering supporters in Kentucky on Tuesday night.
"While we continue to go toe-to-toe for this nomination, we do see eye-to-eye when it comes to uniting our party to elect a Democratic president in the fall," she told an audience in Louisville. "We will come together as a party united by common values and common cause, united in service to the hopes and dreams that know no boundary of race and creed, gender or geography, and when we do, there will be no stopping us."
Tuesday's results may explain the election-night locations of the two Democratic candidates. Clinton gave her victory speech in Kentucky, dodging Oregon, where Obama is expected to win handily.
Obama will also skip Oregon to appear in Iowa, the site of the campaign's opening contest, a caucus that he won, and where he will celebrate clinching a majority of pledged delegates.
There are 3,253 pledged delegates, and even if he has a poor showing in both Tuesday primaries, Obama should easily top the 1,627 delegates needed to make that claim.