The big problem in finding a conservative challenger to run for the GOP nomination is not the absence of a genuine constituency, nor is it even enthusiasm for ex-New York City Mayor Rudy Giuliani. Right-wingers who would pass the litmus test — guys like former Arkansas Gov. Mike Huckabee, Kansas Sen. Sam Brownback, Colorado Rep. Tom Tancredo, California Rep. Duncan Hunter, former Health and Human Services Secretary Tommy Thompson, or even ex-Tennessee Sen. and famous actor Fred Thompson — face the need to climb over the political corpses of former Speaker New Gingrich (Ga.) and ex-Massachusetts Gov. Mitt Romney to make their case.

The purist pro-life, pro-gun, anti-gay believers who used to dominate the Republican primary are still so focused on other candidates that they can’t turn their attention to one of their own. They lament Sen. John McCain’s (Ariz.) apostasy on issues like taxes, campaign-finance reform, global warming, and terrorist interrogation and can’t concentrate on supporting an alternative.

Romney, who is panting after their support, is a political duck decoy, distracting onlookers from focusing their gaze on the real conservatives who might run. He can’t win. He can’t get nominated or even become the consensus candidate of the right wing. He’s too Mormon (it shouldn’t be an issue, but it is) and flip-flop-flipped from pro-life to pro-choice and back again. These problems, combined with his flip-flops on gay rights and stem cell research, make him incapable of becoming the right-wing candidate to oppose Giuliani.

Newt Gingrich still sends thrills down Republican spines but won’t say whether or not he’s running until the fall of 2007. By that time, Rudy will probably have $40 million or $50 million in the bank and will be en route to triple digits. Newt is a bright guy who must know that the convergence of primaries on Feb. 5 makes a late entry politically unfeasible. So I don’t think he’s running.

But neither McCain, as he fades, nor Romney, as he sputters, nor Gingrich, as he waits, are getting out of the way to let right-wingers attract support. These three well-known candidates are standing in the way, blocking one of the lesser-known candidates from emerging.

The situation conservative Republicans face in 2008 is a lot like that which faced moderate Democrats in 2004. While the left of the party was amply represented by John Kerry and Howard Dean, four moderates — John Edwards, Wesley Clark, Joe Lieberman, and Dick Gephardt — vied for attention and support.

In 2008, unless Romney and Gingrich get out of the way, the conservatives won’t be able to come up with a candidate until it is too late to raise the money to beat Giuliani in the more than 20 states that will hold their primaries on Feb. 5. Only then can the conservatives who are both acceptable and can actually win emerge from the pack and become a challenger to Rudy.

Who will have the best chance once the smoke clears? Fred Thompson is clearly the best-known, but it is easier to go from being a politician to an actor than it is to move in the other direction. After seeing Thompson play the role of a semi-hapless conservative New York district attorney so convincingly, it will be hard for voters to see him as the president.

Mike Huckabee (a former client) has an originality and creativity that will make him very attractive. He speaks, for example, about the need to control Medicaid and Medicare costs not by budget cuts but by cuts in smoking and obesity and an increased commitment to exercise. He focuses on the need to enhance education with a focus on music and art to stimulate creativity and help students compete as the entertainment industry becomes increasingly important in our economy. Sam Brownback did well in the National Conservative Political Action Committee straw poll and is showing some signs of movement; Tancredo, meanwhile, has a good issue — immigration — to ride.

But nobody is going anywhere with the bodies cluttering the road in front of them.