Could someone who isn't currently among the Republicans battling for the nomination get it? Nate Silver discusses what Sarah Palin or Chris Christie or someone else would have to do to jump into the fray now and emerge victorious. Bottom line: It's possible but it would be very, very difficult. My guess is that anyone who genuinely imagines themselves in the Oval Office and yearns for that would think they'd do better to wait 'til next time.