Both Sens. Barack Obama, D-Ill., and Hillary Clinton, D-N.Y., are in a dead heat with McCain, the presumptive GOP nominee, the CNN/Opinion Research Corp. poll said.

If Obama were to win the nomination, he would get 47 percent of the vote compared to 46 percent for McCain, statistically a tie when factoring the poll's 3-percentage-point margin of error.

If Clinton is the Democratic nominee, the CNN/Opinion Research poll indicated she would get 49 percent of the vote, compared to McCain's 47 percent -- again, a statistical tie.

While Clinton and Obama match up well against McCain, CNN Polling Director Keating Holland said ifferent groups of voters were supporting the two Democrats.

"Clinton appears to do a little bit better than Obama among older voters, women and self-identified Democrats against McCain; Obama's numbers may be slightly better among younger voters and those who describe themselves as Republicans and Independents," Holland said.