Exit Polls: Obama Makes Big Gains in Clinton's Core Support

There were other examples of McCain's continued challenges in the Republican base. Forty-two percent said he's "not conservative enough."

Voters by a wide margin were most attracted to a candidate who "shares my values," and Huckabee won them by 53-36 percent.

And Republicans who most strongly oppose abortion, saying it should be illegal in all cases, went for Huckabee by more than 2-1, 64-30 percent

At the same time McCain easily prevailed as the candidate most likely to improve U.S. relations with the rest of the world, and, by a 6-1 margin, as the one most likely to beat the Democratic nominee in the general election in November.