WASHINGTON — The lack of widespread Republican condemnation of President Trump for his comments about four Democratic congresswomen of color illustrated both the tightening stranglehold Mr. Trump has on his party and the belief of many Republicans that an attack on progressivism should in fact be a central element of the 2020 campaign.

While a smattering of Republicans chastised Mr. Trump on Monday, most party leaders in the House and Senate and much of the rank-and-file remained quiet about the president’s weekend tweets directing dissenters to “go back” where they came from. He followed up on those comments on Monday with harsh language directed at “people who hate America” — an inflammatory accusation to be leveled against elected members of the House.

With Mr. Trump far more popular with Republican voters than incumbent Republican members of Congress, most are loath to cross the president and risk reprisals. The case of Representative Justin Amash, the Michigan lawmaker who was forced to leave the party after he dared to suggest Mr. Trump should be impeached, serves as a cautionary tale.

At the same time, many Republicans are seeking to label the four congresswomen and their ideas as “far left,” seeing it as a potential foundation of a sweeping critique of Democrats in 2020. In an appearance on Fox News, Senator Lindsey Graham, Republican of South Carolina, called the four “a bunch of communists,” a step beyond the president, who said he was at the moment only willing to go so far as calling them “socialists.”