I noticed that the NASA administer recently said that Project Prometheus was fully funded. I would imagine that members of Mars Society are pretty excited by this. I did web search and found this article:
http://www.thespacereview.com/article/32/1
"Technology is not the only challenge Prometheus faces. By invoking the “n-word”—nuclear—Prometheus faces a number of political and regulatory issues, ranging from extensive environmental reviews to concerns by anti-nuclear activists and the wider public about the dangers of a nuclear-powered spacecraft. Activists, for example, tried to block the launch of Cassini, which carried a relatively small amount of plutonium in heavily-shielded RTGs; one can imagine their reaction to the launch of a spacecraft carrying a nuclear reactor with a larger amount of uranium. In the wilder imaginations of some, Prometheus is seen as a stalking horse for military space nuclear power applications and the “weaponization” of space.

However, the political hurdles for Prometheus, at least in Congress, may not be as high as some fear. Kristin Svinicki, senior policy advisor to Senator Larry Craig, a proponent of nuclear power in general, said she noticed broad bipartisan support for Prometheus at a hearing about the program earlier this year. “There were senators who showed up who I didn’t even know were on that subcommittee because they never came to hearings,” she said, “who came for the specific purpose of telling the [NASA] administrator, ‘This is a good business for you to be in, and we want to support you.’”
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