If the 'Rats do capture the House, they might be able to push through impeachment if they can enforce rigid party discipline (and maybe pick up a RINO or two), but it's highly unlikely they could come close to a conviction in the Senate (that would require a lot of Republican senators to vote against Bush). The goal might be just to get a higher number of senators to vote for conviction than voted to convict Clinton...it's mainly about payback (and weakening the President).
Kuhl is considered highly vulnerable. Pres. Bush visited his district in March for a Social Security town hall meeting, at Kuhl's request. There's lots of local media attention to these under-the-MSM-radar daily events.