WASHINGTON — The fragile bipartisan consensus that nuclear power offers a big piece of the answer to America’s energy and global warming challenges may have evaporated as quickly as confidence in Japan’s crippled nuclear reactors.

Until this weekend, President Obama, mainstream environmental groups and large numbers of Republicans and Democrats in Congress agreed that nuclear power offered a steady energy source and part of the solution to climate change, even as they disagreed on virtually every other aspect of energy policy. Mr. Obama is seeking tens of billions of dollars in government insurance for new nuclear construction, and the nuclear industry in the United States, all but paralyzed for decades after the Three Mile Island accident in 1979, was poised for a comeback.

Now, that is all in question as the world watches the unfolding crisis in Japan’s nuclear reactors and the widespread terror it has spawned.

“I think it calls on us here in the U.S., naturally, not to stop building nuclear power plants but to put the brakes on right now until we understand the ramifications of what’s happened in Japan,” Senator Joseph I. Lieberman, independent of Connecticut and one of the Senate’s leading voices on energy, said on CBS’s “Face the Nation.”