At this point Mitt Romney has two advantages in the Republican primary. Most people know who he is and they don’t automatically think he would make a terrible president. This puts him in better shape than the rest of the field. From Pew:
Of the party’s best-known possible candidates, only Mitt Romney has broad potential appeal. Large majorities have heard of four possible Republican candidates – Romney, Sarah Palin, Newt Gingrich and Ron Paul. But most who have heard of Palin and Gingrich say there is no chance they would vote for them (63% each). About as many (60%) say there is no chance they would support Paul.
By contrast, far fewer voters (44%) who have heard of Romney have ruled out voting for him, while 51% say there is at least some chance they could support the former Massachusetts governor.
Normally I would assume no one would be foolish enough to attempt to run for office if a large majority of the electorate had already decided they would never vote for him/her, but that problem has not stopped either Newt Gingrich from running nor Sarah Palin from seriously considering it.
Look at how electable Romney appears in this poll, it is no wonder Democrats are going all out to try to kill Romney in the primary with their healthcare death hug.