Hillary Clinton weighed in this week on a question that has plagued Senate Democrats and much of the party for months: whether Sen. Dianne Feinstein of California should resign in light of mounting health problems that have made it difficult for her to do her job.

Ms. Clinton’s answer was no, but it was based largely on anticipation that Republicans would seize the vacancy, not on an assessment of Ms. Feinstein’s health or performance.

“Here’s the dilemma: Republicans won’t agree to add another person to the Judiciary Committee if he steps down,” he told Time magazine on Monday, in an interview published Tuesday night. “I want you to think about how horrible that is. I don’t know in her heart if she would really do it or not, but right now, she can’t. Because if we’re going to get judges confirmed, which is one of the most important ongoing obligations we have, then we can’t afford to have their vacant position.”

Ms. Clinton suggested that her answer might be different “if Republicans said and did things decently”. But she, she added, “won’t say that.”

Ms. Feinstein is recovering from shingles, encephalitis and Ramsay Hunt syndrome, all of which kept her out of the Senate for more than two months until early May. She has also been experiencing memory loss and faced some calls to quit even before her latest health issues. But it was her recent absence, which prevented Democrats from advancing some judicial nominations, that caused those calls to spread from most left-wing voters to even some fellow Democrats in Congress.

Responding to mounting pressure, Feinstein asked in April to be temporarily replaced on the Judiciary Committee, but Senate Republicans refused to allow it.

It’s unclear whether Republicans would continue to hold the vacant seat if Ms. Feinstein resigned. At least one Republican senator who opposed a temporary replacement, Senator Lindsey Graham of South Carolina, has said I would support a permanent replacement. And refusing to fill an official vacancy would be a greater breach of precedent than refusing to fill an informal vacancy.

But given the precedent set by Senate Republicans themselves: They refused to allow President Barack Obama to fill a Supreme Court vacancy in 2016 on the grounds that the upcoming election was too close, and then allowed President Donald J. Trump will fill vacancies even closer to the 2018 and 2020 elections: Ms. Clinton’s concern is not unfounded.