Their numbers are dwindling now, the faded yellow newspaper clippings reporting their childhood trips to the hospital tucked away in family scrapbooks. Iron lungs, the coffin-like cabinet respirators that kept many of them alive, are a thing of the past, relegated to history books and museums. Some feel the world has forgotten them.

Now the nation’s polio survivors are reliving their painful memories as they watch events in Washington, where the Senate will soon consider the nomination of Robert F. Kennedy Jr., a fierce critic of vaccines, to be the nation’s next health secretary. And they are keeping a close eye on one of their own: Senator Mitch McConnell, the former Republican leader.

It has been nearly 70 years since Dr. Jonas Salk’s polio vaccine was pronounced “80 to 90 percent effective” against the paralytic form of the disease. Although the government does not keep official numbers, advocacy groups say there are an estimated 300,000 survivors in the United States. Mr. Kennedy’s nomination has prompted some to speak out.

The movie director Francis Ford Coppola recently recalled being in a hospital ward “so crammed with kids that there were gurneys piled up three and four high in the hallways.” The actress Mia Farrow, infected when she was 9, posted a picture of a room filled with iron lungs on Instagram with the caption: “No RFK Jr. we cannot go back to this. # polio.”

Representative Steve Cohen, Democrat of Tennessee, the only other polio survivor in Congress, called pointedly for the Senate to reject the nomination. “I believe I have a duty to speak out for all who have had polio — from those lightly affected to those who lived in iron lungs and died,” Mr. Cohen said in a recent statement.