The fact - FACT - is that Romney did not turn out the base. He got fewer votes than McCain (at least in population-adjusted terms). Obama lost millions of votes from last time, but Romney still managed to lose because people who would have voted for a Republican candidate did not bother.
Recall that McCain's performance was less than it should have been as well, despite being comparable to Bush's blase performance.
The lesson learned here is that in the future, the GOP will have to run an inspiring candidate to win the Presidential election. In order for the candidate to be inspiring, he/she will have to be rock solid in terms of liberty and free market principles. Period.