I don't know that Obama has ever been opposed to nuclear power, but he did state explicitly during his campaign that he is not a proponent of it. Apparently that has changed -- check these quotes:
Two years ago during his campaign: (see the video)
"I start off with the premise that nuclear power is not optimal, and so I am not a nuclear energy proponent. Until we can make certain that nuclear power plants are safe, that they have solved the storage problem, until we solve those problems and the nuclear industry can show that they can produce clean, safe energy without enormous subsidies from the U.S. government, I don’t think that’s the best option." (December 30, 2007)
Last week at the State of the Union address:
"But to create more of these clean energy jobs, we need more production, more efficiency, more incentives. And that means building a new generation of safe, clean nuclear power plants in this country. (Applause.) It means making tough decisions about opening new offshore areas for oil and gas development. (Applause.) It means continued investment in advanced biofuels and clean coal technologies. (Applause.) (January 27, 2010)
So that's the clean energy plan -- nukes, oil, gas, coal and advanced biofuels? Get a clue, man! The enthusiastic applause from the gallery should be your clue that the fix is already in on nukes. That, despite the fact that MoveOn determined that his call for new nuke plants was the low point of the speech in the public's eye.
Congress just voted to give the nuclear power industry another $54 billion in loan guarantees, so the plan is to start building in 2011.