At his blog Frontloading HQ, political scientist Josh Putnam notes that, after Florida, it becomes impossible for a candidate to enter and win the 1,144 delegates necessary to attain the Republican presidential nomination:
If the list is constrained more simply to the states where filing deadlines have not passed, the total delegates open to a late entrant drops to 1157. After Tuesday, when Kentucky's (and Indiana's petition-see footnote 17 above) deadlines pass that total will drop below 1144 to 1066.
That's not to say that a candidate couldn't win enough delegates to force a brokered convention, but-as Putnam asks-who is that candidate? To be successful, a late entrant needs to have considerable fundraising and organizational ability, a national constituency, and a message that can appeal to a broad swath of the Republican Party. Logistical difficulties aside, there is no one in the GOP who fits that bill and could cruise into the nomination race and "save" Republicans from their current candidates.
As it stands, a fair number of Republicans don't seem to want saving. Jonathan Chait points out that conservatives are beginning to reconcile themselves to a Romney nomination:
One interesting aspect of Romney's impending triumph is that he has consolidated the support of extremely right-wing elements within the party. You can see this as both a cause and a result of his victory - a cause in that he has successfully eaten into the natural base of a right-wing challenger, and a result, in that his ascent has helped portray him as a more natural Obama-slayer
If and when Romney cinches the nomination, Republicans will rally to his candidacy, and we'll quickly forget this odd period where a few conservative activists pined for a white knight to rescue their party.
