On several key votes over the past few years, Nuclear Regulatory Commission chair Gregory Jaczko was the lone voice for tougher industry standards—and now he has resigned, following an intense character assassination campaign.

Jaczko put out a generous and neutral statement this morning: “After an incredibly productive three years as Chairman, I have decided this is the appropriate time to continue my efforts to ensure public safety in a different forum,” he said. “This is the right time to pass along the public safety torch to a new chairman who will keep a strong focus on carrying out the vital mission of the Nuclear Regulatory Commission.”

But that belies a much uglier history. You may recall that late last year, Republicans hauled Jaczko before Congress to answer questions about his supposed brutish behavior as chairman: intimidating and bullying staff, particularly female members, and keeping the other commissioners out of the loop.

But Representative Ed Markey, for whom Jaczko used to work, put together a report on the turmoil that painted a different picture. Instead of uncovering abusive behavior—which still hasn’t been documented—Markey’s staff detailed how in the wake of the Fukushima disaster in Japan, the four other NRC commissioners teamed up to slow down safety responses being designed by Jaczko. It also found “high levels of suspicion and hostility directed at the chairman” from the other four commissioners.

The charge was led by commissioner William Magwood, who spent many years in the nuclear industry—including for the same company that ran the Fukushima Daiichi plant in Japan, as Huffington Post’s Ryan Grim reported at the time. Magwood’s point person, Grim notes, was a then-GOP Senate staffer who is now the top nuclear industry lobbyist.

The supposed turmoil made public by Magwood and the other commissioners was eagerly taken up by Congressional Republicans during those December hearings. “I think you should resign,” Representative Jason Chaffetz, a Tea Party favorite from Utah, told Jaczko after a rapid-fire series of questions during which he repeatedly cut off Jaczko mid-reply. “If you’re going to do the right thing for this country and this commission, you should step down.”

Now, he has. And Republicans eagerly danced on his grave today. “Dr. Jaczko’s troubling behavior as chairman of the Nuclear Regulatory Commission had clearly resulted in a hostile work environment for women that ran counter to acceptable norms of workplace equality and that threatened to undermine the mission of the NRC itself,” said Senate Minority Leader Mitch McConnell in a statement.

“The resignation of Chairman Jaczko will close an ugly chapter and allow the Nuclear Regulatory Commission to focus on its mission—ensuring the safe operations of the nation’s nuclear plants,” said Representative Darrell Issa.

But not everybody was pleased. Vermont Senator Bernie Sanders called out the smear campaign in a statement: “For his efforts to hold the nuclear industry accountable, Chairman Jaczko was subjected to repeated personal attacks made by some of his colleagues and pro-industry advocates in Congress,” Sanders said. “I am extremely disappointed he is leaving the Commission.”

Public interest groups were outraged as well. “News today of Nuclear Regulatory Commission Chair Gregory Jaczko’s pending resignation is a terrifying example of industries trying to wreak havoc on those who regulate them—and winning,” said Tyson Slocum of Public Citizen. “Jaczko sought to create tougher rules for the nuclear industry in the wake of Japan’s Fukushima disaster last year. But the nuclear industry wanted Jaczko gone from Day One. Jaczko stood alone.”