Thousands of people protested across the country on Thursday in support of the inquiry led by Robert S. Mueller III, the special counsel investigating Russian interference in the 2016 election, just one day after President Trump shook up the agency overseeing it.

The demonstrations, seen in the video above, took place in New York, Washington, Boston, Philadelphia, Omaha, Salt Lake City and elsewhere. They came after the president’s firing of former Attorney General Jeff Sessions, who had recused himself from the investigation, much to Mr. Trump’s frustration. The acting attorney general, Matthew G. Whitaker, is a Trump loyalist and an outspoken critic of the investigation.

“This is a man who should have recused himself,” said Gerald Harris, a retired judge who participated in the protest in New York. “It’s simply a sham that he’s going to become the attorney general in charge of this probe.”