White evangelical Protestants, a key support base for the Republican Party, still have not united behind a single candidate for the 2008 White House race, according to a new poll released on Wednesday.

The poll by the nonpartisan Pew Research Center found that former New York Mayor Rudy Giuliani, Arizona Sen. John McCain and former Tennessee Sen. Fred Thompson each drew about 20 percent of the support from this group. Giuliani was on top with 23 percent, followed by Thompson with 21 percent.

Former Arkansas Gov. Mike Huckabee and former Massachusetts Gov. Mitt Romney were each favored by about 10 percent of the white Republican and Republican-leaning evangelicals polled in the survey of over 2,000 U.S. adults from Oct. 17-23.

The results stand in sharp contrast to a straw poll of self-styled "values voters" almost two weeks ago, which put Romney and Huckabee at the top of this heap at around 27 percent each.

Giuliani didn't even get 2 percent of the ballots cast at that conference of religious conservative activists but the latest Pew poll and others suggest he has made strong inroads with this group despite his support for abortion rights and gay rights -- positions anathema to this wing of the party.

Analysts have said Giuliani has managed to win some converts among this core Republican group by pledging to appoint conservative justices to the Supreme Court and by his tough-guy stances on crime and the war on terrorism and his strong support for Israel.

"His strong support for Israel and his generally hawkish foreign policy statements ... appeal to religious conservatives," said Scott Keeter of the Pew Research Center.

McCain and Thompson also did far better in this survey than they did in the straw poll, which could give their campaigns much needed lifts.

But solid support from this group, dubbed the "religious right," remains elusive and is seen as one reason why the Republican race for the presidential nomination is still wide open.

Most of the Republican candidates have some flaws in the eyes of this group.

Romney's Mormon faith and recent conversion to the anti-abortion cause is viewed with suspicion by many evangelicals. McCain dismissed the religious right as "intolerant" during the 2000 campaign. And Thompson has not been totally convincing as a conservative.

The Pew survey also found that a solid majority of Republican white evangelicals or 55 percent said they would at least consider voting for a third party candidate if the election was between Giuliani and Sen. Hillary Clinton, the Democratic front-runner who is also supports abortion rights.

The Pew poll had a margin of error of 2.5 percentage points.