The basic lay of the land for the 2012 election seems to be as follows. Barack Obama has done some things (e.g. the Affordable Care Act) that Republicans hate but that are basically a wash electorally. Most Americans like him personally. The economy seems to be slowly improving, and if it continues on that path, things will look pretty good 18 months from now, making his re-election highly likely. And the Republican candidate, whoever he or she is, will have spent the primaries embracing a series of profoundly unpopular positions, and will therefore spend much of the general election on the defensive about what an extremist s/he either has always been, or has become.
In every presidential election, candidates have to prove their ideological bona fides to their party's base. But the rise of Tea Partyism has made the litmus tests for GOP candidates extraordinarily exacting. This will manifest itself even on issues where Tea Partiers may not have articulated much of a position. Whenever they get asked about something, the candidates' default impulse is going to be, "I don't know what primary voters are thinking about this, but I had better just take the most conservative position possible." Let's take one example: There are now four potential candidates -- Tim Pawlenty, Mike Huckabee, Haley Barbor, and Rick Santorum -- who have come out and said they support re-installing "Don't Ask, Don't Tell" and the ban on gays serving in the military. In case you didn't know, the removal of the ban is proceeding without any difficulty, the fears of Republican congressmen notwithstanding. And according to recent polls, anywhere from two-thirds to three-quarters of the American public supported DADT repeal. Why haven't Mitt Romney and the other candidates demanded DADT reinstallation? One reason: They haven't been asked yet. When they do, you can bet they'll fall in line.
It isn't that all that many voters are going to decide their votes on this issue. But combine it with things like the fact that all the candidates basically endorsed Paul Ryan's Medicare-dismantling budget, and you'll get an evolving narrative about a Republican candidate representing an extremist ideology and a crazy party base obsessed with things like Obama's birth certificate.
The best Democratic strategy may be to get all these candidates on the record on as many issues as possible before the general election begins.