Neither will go anywhere. It's going to be hard to pin anything on Bush, really. The argument that the war (has it even been declared a war in Congress?) is illegal is one that can be argued back and forth, and won't stick to Bush. Yeah, he's a crappy President. Yeah, his administration is largely responsible for the war and our economic problems, but to impeach requires a solid evidence against the President, not his administration. Nobody in Congress is going to impeach a President unless they think they'll get an impeachment.
Also, who in their right mind decides just now that Bush sucks? Like, "ALRIGHT, IT'S 2008 - WE'VE HAD ENOUGH!"