The former mayor wasn’t well. Mayor John V. Lindsay had cut a dashing figure during his tenure, but after he left office in 1973, his health declined precipitously, while his law career faltered. Help arrived from an unlikely source.

Rudolph W. Giuliani, the former prosecutor who led New York in the 1990s with a tough-on-everything approach that had rebuked Mr. Lindsay’s liberalism, was now the mayor. He would ensure that Mr. Lindsay could receive municipal health insurance coverage in the final years of his life.

“All of us were grateful for Rudy’s kindness,” said Steven L. Isenberg, who served as chief of staff to Mr. Lindsay. “The need was real.”

The episode is resonant today as Mr. Giuliani’s own health deteriorates, leading him to seek medical care covered by the World Trade Center Health Program for people affected by the Sept. 11, 2001, terrorist attacks.

Mr. Giuliani was in the final months of his mayoralty when the attacks happened. He was a frequent presence at ground zero, the site of the fallen World Trade Center towers, where the air was rife with toxic dust and smoke that have been linked to respiratory problems.