Well in Michigan he tied Santorum but the state GOP changed the rules after the fact and gave the win to Romney.
That kind of thing helps.
In Virginia, the nomination rules blocked all but 2 candidates.
In Florida, who voted early, and was supposed to have half of its delegates not seated... well, that was just ignored.
Lots of hanky panky going on, not to mention Rove and machine badmouthing conservatives with the support of the MSM.
/johnny