This article is part of David Leonhardt’s newsletter. You can sign up here to receive it each weekday.

In a newsletter last year, I quoted the economist and author Robert H. Frank calling Steve Bullock “the most important person on the planet.”

Bullock, the two-term governor of Montana, is the only Democrat with a decent chance of winning the U. S. Senate election there this year. But Bullock had been insisting he would not run. Without him in the race, the Democrats’ chances of retaking the Senate would be significantly smaller. And only if the Democrats control the Senate, the House and the White House in 2021 is there any prospect of major action to combat climate change.

“The window of opportunity for effective action on the climate crisis is rapidly closing,” Frank argued. “Absent robust measures to curb greenhouse gases, climate scientists forecast steadily more frequent and intense storms, droughts, flooding, and wildfires. Alone among major political parties worldwide, Republicans have refused even to admit the existence of climate change, much less enact meaningful legislation for dealing with it.”