In the last three months alone, three Democratic House members have died in office, former President Joseph R. Biden Jr. announced a serious cancer diagnosis and a new book stoked fresh scrutiny of his declining abilities while serving as commander in chief.

For a party struggling with a litany of problems, perhaps no subject in recent years has been more painful, delicate or politically perilous than the matter of age — an issue that keeps rearing its head in 2025 as party leaders now acknowledge the problem but remain hesitant to directly call out aging colleagues.

The subject arose yet again on Wednesday, as the family of Representative Gerald E. Connolly, a Democrat from Virginia, announced that he had died at 75. He was the sixth House Democrat to die in office in the last year or so, according to what the House press gallery calls its “casualty list” of deaths, resignations and retirements.

Just a few months ago, Mr. Connolly beat out one of the youngest members of Congress, Representative Alexandria Ocasio-Cortez of New York, 35, in an internal contest to lead their party on the House Oversight Committee. He said at the time that the idea that there was generational change underway in the caucus was a “false narrative.”

His death, after a public battle with esophageal cancer, prompted an outpouring of grief from colleagues. But as Democrats strain to project energy in fighting President Trump, some in the party also saw it as another harsh reminder of the risks the party faces when it prizes seniority and loyalty above all else.

Former Representative Joe Cunningham, 42, a South Carolina Democrat, supports age and term limits for political office and publicly urged Mr. Biden not to seek re-election. In an interview, he spoke warmly about Mr. Connolly.