How many?

Obama has spent the past week letting down his most rabid constituencies: so far gays (no more support for gay marriage) and hispanics (path to legal status not citizenship). He's sounding more like Romney than the old Obama -- and a good thing too!

Could Obama be preparing to step aside in case it goes that way, and acting now to prevent any such rioting?

Well I think it's more likely the face of Obama will continue to occupy the office, but he will have to take some directions (maybe a lot of directions) from Romney, a sort of hidden "coalition government" as if we're a Parliamentary system.