The media/press. The media will be on impeachment like flies on poop in the middle of the summer. Why give the left ANY reason to galvanize their base when their actions are depressing it.
Lets win this year and then reevaluate what can be done. If the US Congress does not do the job they are elected to do, there is no way that same congress will impeach or convict 0bama.
You say it like it is a bad thing. We have found it galvanizes your base and wins elections. You give the media far more credit than it deserves. In 2014 it is about getting your people to vote, nothing else matters. What a better motivator than your side fighting back?