Romney can appeal to the moderates and independents and the current president has very little to offer those groups in terms of accomplishments or potential going forwrd, Ryan energizes the conservative base and he's very impressive....still trying to figure out why the current president picked Joe Biden aside from making him look really smart in comparison.....
maybe he listened to David Frum?
"Conservatives remain skeptical about Mitt Romney, but he is still the only candidate who even has a chance of winning the general election.
The key is that Romney is the only candidate who can potentially appeal to moderates.
Even if there is no conservative enthusiasm, the underlying numbers still make Romney the best possible nominee. Because Democrats have a statistically smaller base, they need moderates more desperately than Republicans.
If conservatives show up to the polls at the same rate as they did for McCain, Romney only needs modest gains among moderates to win the election."
Hey Romney, Don't Forget to Pander to Moderates - The Daily Beast