Did John McCain just rescue a big part of Obama’s climate legacy to punish Trump for firing Comey?

In a big, pleasant surprise for environmentalists, the Republican-controlled Senate on Wednesday failed to repeal an Obama-era regulation that prevented leaks of natural gas on public lands. The vote was always going to be close—all Senate Democrats and two Republicans openly opposed it—but at the last minute, the senior senator from Arizona stepped in and cast the tie-breaking vote against repealing the regulation.

The Bureau of Land Management’s methane waste reduction rule was (and now still is) a large part of Obama’s effort to fight climate change, because it prevented oil and gas companies from venting, flaring, and otherwise releasing large amounts of methane from their operations on federally-owned land. Methane is the main component of natural gas and a powerful greenhouse gas, 86 times more potent than carbon dioxide.

Republicans were trying to overturn the rule under the Congressional Review Act, which requires a majority (51 votes) to be successful. With Republican senators Susan Collins and Lindsey Graham already against it, the vote would have been 50-50. The time in which the Senate is allowed to use the CRA is about to expire, so they will not be able to use it to repeal the rule in the future.

McCain’s vote made Republicans’ failure decisive—and raised questions about his motives. Minutes before casting his unexpected “no” vote, McCain criticized President Donald Trump for his surprise firing of FBI Director James Comey, saying Trump had not provided sufficient rationale. A C-SPAN video from the minute before McCain cast his vote shows him in an apparent disagreement with Republican colleague John Cornyn before abruptly voting and walking out of the chamber. McCain later said his vote was motivated by his desire to “reduce pollution.”

Whatever the reason, environmental and public health groups rejoiced. The American Lung Association called the vote “a victory for public health and safety,” while the League of Conservation Voters deemed it “a victory for all those who are raising their voice in resistance to the anti-environmental Trump administration, Republican leadership and Congress.” But as always, the victory comes with a side of caution. “While we have beaten back this attack on the BLM methane rule, we know that Trump and his Big Oil cronies are eyeing other avenues” to weaken pollution rules, said Friends of the Earth climate campaigner Lukas Ross. “We will continue to fight against any efforts to endanger the future of our lands and our climate.”