President Obama told us recently that his views on gay/lesbian rights have evolved to the point where he believes "personally" that they should have the right to marry. This revelation may be late in coming, and it may do little more than acknowledge a trend and its inevitable outcome, but the LGBT community has given him some credit (and some political donations) for the political risk he runs in outing this view.
IS there a political risk? I'd argue that it's very small at this point. Personally, I believe the Obama campaign, and/or the President personally, have recognized that they can bolster their standing with a significant element of the "base" constituency without really harming themselves with the right-wing voters. Especially when he continues to say that actual legislation on the subject is a matter for the states. There could be some concern about African-American voters, yet early indications are many accept the President's pronouncement with relative equanimity.
On the other hand, conservatives who oppose gay marriage undoubtedly already "know" that Obama has a secret plan to push through all sorts of pro-LGBT legislation (just as they "know" he's a Muslim, a socialist, and wasn't born in the U.S.). He has little to lose with this group.
In between, however, is a great mass of voters who may not deeply care about these issues, but who would probably say when asked that it's a matter of fairness and marriage should be available to all. These are also the people who will see that the President's personal view does not necessarily translate into a flurry of legislative proposals. With this group, I suspect the Obama position sounds a lot more reasonable and human than his opponents'.
This attitude on the part of the "typical" voter or political independent could be the basis of a cleverly conceived political trap in Obama's recent statement. Romney appears to have recognized this by not making a big deal of Obama's announcement. Others have not been so circumspect. Firebrand conservatives gleefully plan to "make this a major campaign issue." If they do, it's quite possible they'll turn off more voters than they turn on with yet another example of their extremist, outside-the-mainstream thinking.
In the long run there may be more risk for Republicans than for Democrats in the President's attitudinal "evolution.'
It's interesting to observe Romney's own evolution (or should I say, how his views were intelligently designed?) on this subject. See the excellent chart comparing the two candidates, and note that this is another matter on which Romney has flip-flopped (though Obama has also).