JUDY WOODRUFF:

Scott Pruitt, the controversial and embattled head of the U.S. Environmental Protection Agency, is out. President Trump announced his resignation this afternoon.

In his departing letter, Pruitt said he was leaving because of — quote — "unrelenting attacks on me personally, my family" that are — quote — "unprecedented and have taken a sizable toll on all of us."

He also praised Mr. Trump for the agenda they had jointly pursued to — quote — "get results for the American people, both with improved environmental outcomes as well as historical regulatory reform at an unprecedented pace."

As William Brangham explains, Pruitt's agenda was the source of deep debate, but increasingly so was his personal conduct in the office.