Greece is in serious trouble due to runaway spending and debt. It is likely that sometime this summer, things are going to get pretty bad in Greece. If that happens, conservative/GOP calls for cuts in spending v. liberal/Democrat desires to spend more money and go further into debt are going to find a much more receptive audience with voters who don't want the U.S. "to go the way of Greece." That could impact not only the top of the ticket, but House and Senate races as well.
The media will claim that Greece tried austerity (a word people will remember hearing, so they’ll “remember” what they’re told) and it failed and that’s why we must have more stimulus.