She said she has “a little chuckle to myself” when she thinks about the current debates over health care. “I don’t know,” Mrs. Clinton said. “Where was he when I was trying to get health care in ’93 and ’94?”

The answer: “Literally, standing right behind her,” a Sanders spokesman, Mike Casca, said on Twitter, posting a photo from a 1994 news conference that shows Mr. Sanders next to Mrs. Clinton when the then first lady spoke about the White House’s proposed health care overhaul.