WASHINGTON — More than half of white evangelical Republicans would consider voting for a conservative third-party candidate should the 2008 presidential race pit Hillary Rodham Clinton against Rudy Giuliani, a poll said Wednesday.

The finding, in a survey by the nonpartisan Pew Research Center, was the latest reading of discontent among one of the GOP's cornerstone voting blocs. Giuliani, the leading Republican contender in most national polls, is a former New York mayor whose views on abortion, gays and guns are considered too moderate by many conservatives.

According to the poll, 55 percent of white evangelical Republicans said they would consider a conservative who ran as a third-party candidate. Forty-two percent said they would not.

Evangelicals comprise 34 percent of GOP and Republican-leaning voters, according to Pew. They are divided about evenly among Giuliani, Fred Thompson and Sen. John McCain of Arizona.

It is unclear whether a third-party bid would be launched should Giuliani become the GOP nominee. Several dozen conservative Christian leaders met privately in September to discuss that possibility, but top evangelicals said they have reached no consensus.

The evangelicals' dissatisfaction reflects a general GOP discontent. According to the Pew poll, Republicans are less likely than Democrats to say that their own party is concerned about people like themselves, can bring needed change or is more honest or ethical.

Overall, 50 percent of Americans identified themselves as Democrats or leaning toward Democrats, compared to 36 percent who consider themselves Republicans or GOP leaners, Pew found. That is the largest gap in almost 20 years of Pew surveys, and a big change since 2002, when the two parties were even at 43 percent each.

Clinton, the senator from New York, leads Democratic contenders in national polls.

The poll involved telephone interviews with 2,007 people conducted from Oct. 17-23. It had a margin of sampling error of plus or minus 2.5 percentage points. That included 648 Republicans and GOP-leaners, for whom the margin of sampling error was plus or minus 4.5 points.