Representative Nadler could face a primary from Lindsey Boylan, a former economic development adviser to Gov. Andrew M. Cuomo. She said she was considering a run after watching the 2018 midterms, as “these women decided not to wait their turn because it was never going to be their turn.”

“I just can’t justify having my daughter watch me sit on the sidelines,” she said.

A huge X-factor in any Nadler primary would be the billionaire activist Tom Steyer, who has pushed for the impeachment of Mr. Trump. Mr. Steyer has already polled the popularity of impeachment in the district and is launching a $200,000 direct mail, television and digital ad campaign this week urging Mr. Nadler to begin impeachment hearings in his committee.

In the Bronx, Representative José E. Serrano, in Congress since 1990, could face a challenge from Councilman Ritchie Torres, a 30-year-old often described as a rising star, who said he is weighing a run. Mr. Serrano, 75, almost faced a primary in 2018: Ms. Ocasio-Cortez initially filed paperwork to run against him before refiling days later against Mr. Crowley.

Two other Democratic New York City congresswomen who faced primary opponents in 2018, Representatives Yvette Clarke and Carolyn Maloney, expect challenges again. Ms. Clarke, who won with only 53 percent of the vote, is likely to face a rematch with Adem Bunkeddeko, the Harvard-educated son of war Ugandan refugees who has signaled he plans to run again.

“We’re at a moment of reckoning. Some people get it and some people don’t,” Mr. Bunkeddeko said. “Maybe someone’s seventh term is the charm?” he added of Ms. Clarke. “But most of us aren’t holding our breath.”

Ms. Clarke said she had reorganized her district office following the 2018 close call and is aggressively selling her progressive credentials in the more gentrified and liberal parts of the district, such as Park Slope. “I definitely will not be caught by surprise,” she said.