WASHINGTON -- New York-based political consultant Kieran Mahoney's statewide survey of probable Republican participants in the 2008 Iowa presidential caucuses shows this support for the "big three" GOP candidates: John McCain, 20.5 percent; Rudy Giuliani, 16.3 percent; Mitt Romney, 3.5 percent. Astonishingly, they all trail James Gilmore, the former governor of Virginia, with 31 percent.

How could that be? Because it was not a legitimate survey, but a "push poll." That normally is a clandestine effort to rig a poll by telling respondents negative things about various candidates. Mahoney makes no secret that his voter sample was told of liberal deviations by McCain, Giuliani and Romney, and of true-blue conservatism by Gilmore (Mahoney's client).

Mahoney is trying to prove a point widely accepted in Republican ranks. None of the three front-line candidates is a natural fit for the nation's right-of-center party. Without question, there is a conservative void. The question is whether Gilmore or any new candidate can fill it.

The most commonly mentioned void filler is not Gilmore but Newt Gingrich. A straw poll by the right-wing Citizens United organization of its political contributors showed Gingrich leading with 31 percent (followed by Giuliani at 25 percent, Romney at 10 percent and McCain at 8 percent). But based on his record as speaker of the House, Gingrich's conservative record is far from flawless.

Mahoney did not include Gingrich in his Iowa poll of Republicans likely to vote in next year's caucuses. It first showed McCain leading with 33 percent, followed by Giuliani with 31.5 percent and Romney with 8.8 percent (and the unknown Gilmore at 1.3 percent). This is a voter sample that described itself as 70 percent conservative and 68 percent pro-life, and gave an astounding 76 percent favorable rating for President George W. Bush.

The polltakers next "pushed" -- alleging information about each candidate that could alienate conservative voters. McCain: opposed tax cuts, favored "amnesty" for illegal immigrants, opposed a ban on same-sex marriages. Romney: "refused to ban" abortion in Massachusetts, committed to "full equality" for gays and lesbians, put health care in the hands of bureaucrats. Giuliani: supported Democratic Gov. Mario Cuomo's re-election in New York, is pro-gay rights and pro-choice, supports gun control.

That additional information dropped Giuliani by 9 percentage points to 22.3 percent and Romney by 5 points to 3.8 percent, while McCain rose 2 points to 35.3 percent. The unknown Gilmore was constant at 1.3 percent.

Then the pushers projected Gilmore as a tax-cutting, jobs-creating governor of Virginia, head of a congressionally appointed commission of terrorism, chairman of the Republican National Committee and National Rifle Association member opposing gun control. With that buildup, Gilmore finished first, well ahead of the field.

That suggests at least the theoretical success of a campaign to knock down the conservative credentials of the big three candidates and build up Gilmore's. "I have the best track record of any of the candidates," Gilmore told me, adding that McCain and Giuliani are "not conservative" while Romney was a "liberal governor of Massachusetts."

With Gilmore a latecomer to the presidential fund-raising game, it is doubtful he could find sufficient funds to tear down his opponents and build up himself nationally or even in the state of Iowa. But he will have plenty of help.

At the Conservative Political Action Conference (CPAC) attracting right-wingers nationwide to Washington this weekend, Citizens United will distribute a 23-page attack on McCain. "He's no Ronald Reagan," it begins, and concludes: "John McCain is not a conservative." (McCain is the only announced Republican presidential hopeful not scheduled to speak at CPAC.) Simultaneously, McCain operatives are putting out material that depicts Giuliani riding into City Hall on the shoulders of the New York Liberal Party as a throwback to the old Tammany Hall Democratic machine.

It is hardly too late for such negative campaigning to tear down Republican front-runners because of inadequate conservative credentials. At this point in the 2000 election cycle, Bush was far in front with 45 percent in the polls, with Elizabeth Dole second at 29 percent, and McCain at a mere 3 percent, behind Dan Quayle and Steve Forbes, before making his run that nearly won the nomination. The GOP lineup for 2008 may still be open, considering the conservative void.