Any decent candidate would have beaten Jimmy Carter II.
Romney has been a failure as a candidate his entire 20 years of running for office, he has always broken spending records, has injected 55 million dollars of his own money at crucial points during his campaigns, and he won a single election for governor, he was rejected for reelection and left that office with 34% approval, Romney then lost to the non-funded Huckabee and old man McCain in 2008, before Carter 2 thumped him in 2012.
Then there must not have been one. Unfortunately, I don't see the situation improving significantly for 2016.