GOP presidential candidate Tom Tancredo said Monday that his campaign will be "pretty much over with" unless he can finish in the top three in either the New Hampshire or Iowa primary contests.

Then, he says he'll decide whether to seek re-election to the House.

Donors will determine the fate of his White House campaign, Tancredo said.

"It's a decision made based upon the people who give you money," he told The Associated Press in an interview. "At a certain point, they stop because they say this just isn't going to work. If I don't do well, it's pretty much over with."

Tancredo remains at the rear of the field, ranking fifth in the latest home-state polls behind Fred Thompson, Rudy Giuliani, John McCain and Mitt Romney.

Still, he said he already has influenced the race by forcing the other candidates to address his signature issue, illegal immigration.

He blamed President Bush and Congress for not doing enough to stop illegal immigrants from crossing U.S. borders by enforcing existing law.

The five-term Colorado congressman, who arrived for the interview on his Harley-Davidson motorcycle, was coy about his political future if he decides to end his presidential campaign.

Tancredo said he would tell his constituents about his plans "the day after the (Colorado) Rockies play their last game."

Tancredo said Bush and Republicans in Congress hurt themselves in last year's election by abandoning their principles by, for example, instituting federal school testing programs that intruded on local control and by promoting trade at the expense of cracking down on illegal immigration.

"You have a Republican Party that hasn't done a Republican thing," he said.