Is there room for another GOP candidate?

THE FINAL 2012 SET: Nate Silver is convinced there's still room for another candidate.

One seismic factor affecting Republicans’ decision is that Barack Obama is now exceptionally vulnerable for an incumbent president. If you’re a Republican and you think you can become president, that’s doubly important for you; not only does it mean that those aspirations are more likely to be fulfilled this time around, it also means that they’re less likely to be realized in 2016 or 2020 because there’s now more chance that some other Republican will already occupy the Oval Office by then. So real estate in the Republican primary field has become more valuable. And, despite Mr. Perry’s entry, there’s still some available for the taking. Not much of it is prime real estate, but like the nooks and crannies of Manhattan, it may still be in demand.

He's right, but in many ways there will always be room for another candidate. Another frontrunner, though? That's another question entirely.