Though I think he under-estimates Palin's fund-raising potential, Daniel Larison runs through some of the that make it most unlikely that Palin can actually win the GOP nomination. And as Daniel says, right now the most probable beneficiary of a Palin candidacy is our old friend Shameless Mitt Romney.
Until now Romney has been tacking towards the nationalist base. But Mitt's not very good at phoney populism and it shows. Put Palin in the race, however, and the equation changes: there's no point in Romney going after the type of voters most attracted to Palin (and, to a lesser extent, Mike Huckabee) which, mercifully for him, might spare Romney the embarrassment of trying, once again, to be something he's not. That would give Romney the space, and the motivation, to focus on what he does best: present himself as the problem-solvig technocrat who knows how to get things done.