WASHINGTON -- The outspoken proponent of a crackdown on illegal immigration said Monday that he would campaign against fellow Republicans who support a path to citizenship for illegal immigrants — even Sen. John McCain.

"If there are candidates who are diametrically opposed to what we're trying to accomplish here, and if there's anything I can do to retard their progress, I will do so," Colorado Rep. Tom Tancredo told The Associated Press.

He acknowledged that McCain meets that description.