I am sure there is more than one reason.
The truth is that it was not going to be as easy as some claimed to take out an incumbent POTUS Obama, after all whoever tried would be beat up in a primary where Obama would not. And Obama had the power to give out freebees in election year to get Dem base voters to vote.
I know Rush convinced his listeners that it would be easy for any of them to take out Obama in 2012.
He started that theme in late 2010 and kept it up till Romney lost, after telling his listeners that Romney would win in a landslide.
No, only a pussy like Romney could have lost to Obama. He was the perfect candidate to lose.