WASHINGTON — President Trump widened his war on critics of color on Monday with new attacks on the Rev. Al Sharpton and other political opponents even as he gathered his own African-American allies at the White House to defend him against charges of racism.

In a third straight day of broadsides against black figures, Mr. Trump denounced Mr. Sharpton on Twitter as “a con man” who “Hates Whites & Cops” and again assailed Representative Elijah E. Cummings and his Baltimore-based district, drawing rebukes from Maryland Republicans as well as Democrats.

Mr. Trump’s determination to intensify the furor rather than move on guaranteed that it would continue to dominate the political debate in Washington and force many of the president’s fellow Republicans to choose whether to stand by him, break with him or, in the case of most, find a way to keep out of the discussion.

[Related: How Trump and Sharpton became the ultimate New York frenemies.]

The president linked the clash with Mr. Cummings to his earlier demand that four Democratic congresswomen of color “go back” to their home countries, and he cast it in electoral terms. “If the Democrats are going to defend the Radical Left ‘Squad’ and King Elijah’s Baltimore Fail, it will be a long road to 2020,” he tweeted. “The good news for the Dems is that they have the Fake News Media in their pocket!”