One out of every seven Democratic party voters was not registered as a Democrat at the beginning of the year, and 60 percent of them cast their ballot for Obama, according to the exit polls.
Sen. Hillary Clinton fared better with voters who made up their mind in the last week, the exit polls showed.
Fifty-eight percent of those voters said they chose the New York senator. That includes voters who made up their mind in the aftermath of last week’s heated Democratic debate.
African-American voters in Pennsylvania supported Obama by a substantial margin. According to exit polls, 92 percent cast their vote for the Illinois senator, compared to 8 percent for Clinton.
Clinton got the support of older voters, with 61 percent of those 65 years or older backing her, according to the polls.
She also received more support than Obama among white males, with 55 percent voting for her.
Clinton on Tuesday acknowledged her White House bid is on the line in Pennsylvania.
“Well, I have to win,” Clinton told ABC. “I believe that’s my task. And I’m going to do everything I can to win.”
A CNN poll of polls on Tuesday suggested Clinton is in a position to pull off the victory over Obama.