Then there must not have been one. Unfortunately, I don't see the situation improving significantly for 2016.
Of course there wasn’t one, that is the topic. Romney was terrible, he and the gope manipulated GOP politics since at least 2006 to get the white, mirror image of Obama as the nominee.
Romney shaped the pool in 2006 by hitting with massive, big donor fund raisers, and telling any potential republicans that he was prepared to devote his personal fortune to the primary, after he failed in spite of all that in 2008 (although he did keep his challengers to minor, unfunded players), all potential 2012 challengers knew that he was still going to dominate 2012, so they sat it out.