That's Jonathan Bernstein's belief:
We’re in an era of partisan presidencies, in which the personality, preferences, and ultimately goals of the person in the Oval Office aren’t nearly as important as what the party thinks. That means, too, that it’s mostly a waste of time trying to figure out whether the real Mitt Romney is the moderate problem-solver who was governor of Massachusetts or the fire-breathing “severe” conservative we’ve seen on the campaign trail over the last few months. What’s far more important is figuring out what the coalition who nominated him and is trying to elect him really wants, because that’s how he’ll actually govern.
I'm with Bernstein. Romney is leading the most powerful radical right party in the West. Both in terms of an aggressive return to Cheneyism abroad, and a domestic program that would slash future entitlements while lowering taxes on the wealthy, he is the figurehead for a very different America than the one we have seen these past few years. Along the same lines, Seth Masket thinks Obama will be constrained by his party, even if he wins reelection:
[P]artisan and electoral constraints on a president are never really gone. At the beginning of a second term, he'd be concerned politically about the 2014 midterm elections, trying to build on Democratic seat shares in the Congress or at least mitigate potential losses. And as 2016 comes around, he'll be thinking about cementing his legacy, which comes most easily when one secures the election of an heir who will protect it. All these motivations will keep Obama from going to far to the left (which could damage his party's nominees) or moving too far to the center (which will anger party activists).