Good Tuesday morning, and welcome back after the long weekend. Here are some of the stories making news in Washington and politics today.

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• President Trump has rolled back environmental regulations, pulled the United States out of the Paris accord and turned the term “global warming” into a punch line. His administration is now seeking to undermine or discard research showing the most dire risks of inaction on climate change.

• The Democratic 2020 field is set, and beneath the surface of a seemingly placid race is a much more volatile contest — a series of primaries-within-the-primary along lines of race, gender, age and ideology.

• Senator Bernie Sanders returned to his home state of Vermont for the first time since he declared that he was running for president, no longer leading in the polls but still displaying his uncompromisingly liberal defiance. (Here is a fact-check of some of Mr. Sanders’s remarks on the campaign trail.)