There used to be a group called the "Republican Liberty Caucus," supporting libertarian policies within the Republican Party. I haven't heard anything of substance from them in years. In fact, the RLC is now led by no-name freaks, the most eminent being a goofy-looking Canadian guy with a wingnut resume. The recent actions of maniacal right-wing Republicans illustrate that libertarians no longer hold any power in the party.
Happily, I've found Democratic Freedom, a web site devoted to a sort of Democratic Liberty Caucus. I still don't think they are a significant power in the dishonest and hate-ridden party of John Kerry and Michael Moore. Seeing the Republicans move so rapidly and decisively away from libertarian principles, however, makes me want to give these guys a chance.