Among Republicans, Romney had the most backing among party insiders, with 20% support, followed by Giuliani with 14%, McCain with 10% and former House Speaker Newt Gingrich of Georgia — who has said he might enter the race in the fall — with 8%.

In a potentially worrisome sign for McCain, just over 1 in 10 RNC members said they would not support him if he won the party's nomination in his second attempt.

"It shows just how much resistance there is within the Republican establishment to McCain and how open the party is to candidates who either aren't very conservative, like Giuliani, or only recently minted conservatives, like Romney," Cook said. "McCain has worked pretty hard since 2000 to be a team player, but these numbers would suggest that there is still a problem for him."

"The DNC and RNC members are not just delegates" to the national nominating conventions, said Charlie Cook, a nonpartisan campaign analyst in Washington. "They are key organizers and opinion leaders. They can help build or kill a groundswell, make a candidate's challenge in a state easier or much harder. They matter a lot."