Alex Massie with has a fun analysis:
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....
This, then, presents Romney with the opportunity to run the campaign he should have run in 2004. He's never going to be an exciting candidate and he should probably cease trying to be such. Putting Palin in the race, however, allows Romney to be Romney without having to pander (too much!) or make a fool of himself by trying to persuade the Palinistas that, deep down, he's one of them.
I buy it. In 2008 Romney seemed over-packaged and not totally ready for the national stage. But Palin could lend him a sense of gravitas.
Basically I think there's no way Palin can win the 2012 GOP nomination. But I completely believe she can win Iowa, and milk that spectacle long enough to make a circus of the GOP primaries.