Because Republicans are all unpopular:
Do you approve or disapprove of President Barack Obama’s job performance?
Approve .......................................................... 47%
Disapprove...................................................... 48%
...
Barack Obama................................................ 47%
Mitt Romney.................................................... 43%
Barack Obama................................................ 49%
Michele Bachmann ......................................... 40%
Barack Obama................................................ 48%
Rick Perry ....................................................... 39%
Barack Obama................................................ 49%
Herman Cain................................................... 38%
Barack Obama................................................ 51%
Sarah Palin ..................................................... 37%
...
Do you have a favorable or unfavorable opinion of Mitt Romney?
Favorable........................................................ 34%
Unfavorable .................................................... 49%
Do you have a favorable or unfavorable opinion of Michele Bachmann?
Favorable........................................................ 30%
Unfavorable .................................................... 49%
Do you have a favorable or unfavorable opinion of Rick Perry?
Favorable........................................................ 25%
Unfavorable .................................................... 35%
Do you have a favorable or unfavorable opinion of Herman Cain?
Favorable........................................................ 27%
Unfavorable .................................................... 35%
Do you have a favorable or unfavorable opinion of Sarah Palin?
Favorable........................................................ 28%
Unfavorable .................................................... 62%
http://www.publicpolicypolling.com/pdf/PPP_Release_VA_726925.pdfObama vs. Romney