House Democrats are considering pushing aside some of their most senior leaders from top posts in the next Congress, driven by a worry that aging members are not up to the task of countering President-elect Donald J. Trump and his loyal Republican allies in Congress.

The debate has grown most intense in recent days as dozens of Democrats have been privately pressing Representative Jamie Raskin of Maryland to challenge Representative Jerrold Nadler of New York for his position as the top Democrat on the Judiciary Committee. They are doing so out of concern that Mr. Nadler will be ineffective in pushing back against any efforts by Mr. Trump to abuse his power.

Mr. Nadler, 77, the dean of New York’s congressional delegation, has made it clear he has no plans to step aside. And while Mr. Raskin, 61, is mulling a challenge, he has not yet decided whether to pursue one, according to colleagues familiar with his thinking who spoke on condition of anonymity to discuss the matter.

“As a New Yorker, I have stood up to Donald Trump my entire career,” Mr. Nadler wrote in a letter to colleagues announcing his run for re-election to the post, in which he emphasized his history of going after Mr. Trump. “When he became president, I led the Judiciary Committee’s efforts to hold him accountable for his various abuses of power, culminating in two historic impeachments.”

Mr. Raskin, a former professor of constitutional law, developed a progressive fan base for his work as the lead impeachment manager against Mr. Trump in 2021 and as the top Democrat on the House committee that investigated the Jan. 6 attack on the Capitol that year. He is seen by many colleagues as more aggressive, articulate and shrewd than Mr. Nadler when it comes to taking on the former and future president.

Former Speaker Nancy Pelosi has been among those privately encouraging him to challenge Mr. Nadler, according to the people familiar with the internal discussions.