Hasty and Ruinous 1972 Pick Colors Today’s Hunt for a No. 2

WASHINGTON — Scott Lilly was a young member of Senator George McGovern’s presidential campaign staff in the summer of 1972, and he remembers the satisfaction he felt when Mr. McGovern chose Mr. Lilly’s home-state senator to be the Democratic Party’s vice-presidential candidate.

But a few days after the convention that nominated Mr. McGovern and his running mate, Senator Thomas F. Eagleton of Missouri, Mr. Lilly said, he came to a realization. “It suddenly struck me out of the blue that they didn’t know,” he said, that the decision to pick Mr. Eagleton had been made without some crucial facts.

And he was right. The information he had felt obligated to share with a top campaign aide several weeks before — that Mr. Eagleton had been hospitalized for mental health issues — had never been passed on. Mr. Lilly’s tip “did not register,” the aide, Frank Mankiewicz, said in an interview this year. “It was a very hectic time. I must have had not two things on my mind, but maybe 80.”...