“Santorum talked himself out of the nomination.”
As did all the conservative alternatives to Romney:
The auditions are just about over. Michele Bachmann, Rick Perry, Herman Cain, Newt Gingrich and Rick Santorum all had their chances to be the conservative champion of the nation. Each blew it in his own special way. They soared like rockets and faded away.
In Santorum’s case, it was this:
Late-breaking voters went overwhelmingly for Mitt Romney in today’s Michigan primary as Rick Santorum’s robocalls to Democratic voters, who failed to turn out in big numbers, apparently encouraging Republicans to turn out to back the former Massachusetts governor.
If you are going to run as a conservative, don’t campaign using Democrat Party talking points: Santorum tried to win Democratic union votes by criticizing Romney for not backing the auto bailout. Since the auto bailout is generally despised by conservative voters, they heard this and abandoned Santorum in droves.