It will be a heavy lift, but Mitt Romney can defeat Obama. He must make the case to Republican voters, since some are just not sold. From Politico's Jonathan Martin:

[T]here is pervasive pessimism among Republicans about Romney’s prospects this fall. It’s apparent in rampant discussions about which Republicans will run in 2016 - talk that obviously presupposes a loss in November - and it’s downright glaring in private conversations with GOP officials on Capitol Hill and in consulting shops across Washington.

And the skepticism about Romney isn’t just a Beltway phenomenon. Rank-and-file Republican voters are also uncertain he can win, though it’s the chattering class that is most bearish.