WashPost-ABC survey finds POTUS ahead of all potential Republican challengers.

Obama/Sarah Palin 55 38
Obama/Newt Gingrich 54 39
Obama/Mitt Romney 49 45
Obama/Mike Huckabee 50 44
Obama/Tim Pawlenty 53 38
Obama/Donald Trump 52 40
Obama/Michele Bachmann 51 39

Conducted April 14-17, error margin 3.5 points.