Some longtime Giuliani intimates point to the death on July 7, 2016 of his longtime best friend and political adviser, Peter Powers, as the moment that Rudy lost his way. Others cite Rudy’s marriage in 2003 to Judith Nathan, his soon-to-be third ex-wife, as transformational. Rudy was a pizza and Diet Coke guy when I met him in 1992. But he became an Upper East Side and Hamptons socialite and, worse yet, a Palm Beach neighbor of Donald Trump.

After his mayoralty ended in 2002, Rudy went to work for what seemed like every rich bad guy and tinpot dictator who called. (So going to work for Mr. Trump made sense.) He charged $100,000 for self-aggrandizing speeches about his heroic leadership after Sept. 11. He became a multimillionaire.

In perfect political symmetry, Rudy Giuliani now does Donald Trump’s dirty work: Vainly trying to cover up the Ukrainian cover-up and attacking a Democratic presidential front-runner, Joe Biden, and his son, Hunter.

Watching and reading Rudy’s ferocious lying for Mr. Trump, whether on Fox or CNN, forced me to re-examine his last 25 years, especially the profiteering from Sept. 11. But Ukraine was the coup de grâce. We who admired him for so long expected much more from Rudy Giuliani and his legacy.