Good Monday morning. Here are some of the stories making news in Washington and politics today. (Note: The evening edition of On Politics With Lisa Lerer is off today for the Presidents’ Day holiday.)

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• President Trump mounted one of the most serious executive branch challenges to congressional authority in decades, circumventing Congress with an emergency declaration. The move left Senate Republicans sharply divided, and it remains to be seen whether they will act collectively to try to stop it.

• Senator Lindsey Graham, the chairman of the Senate Judiciary Committee, vowed to investigate whether top officials at the Justice Department and the F.B.I. had plotted an “attempted bureaucratic coup” to remove Mr. Trump from office.

• Bernie Sanders struggled with black voters in 2016, in part because of turmoil between top aides and African-American staffers. Winning the crucial black vote in the diverse 2020 field could prove even harder.