In the eighties, nineties and early 2000s, Rudy Giuliani was considered a serious force to be reckoned with.

He made his name as a hard-charging attorney general in the eighties, leading the federal prosecution of New York City mafia bosses as U.S. Attorney for the Southern District of New York. Although he lost his first election to become mayor of New York, he succeeded in 1993 and held two terms in that office. During those eight years, Giuliani was credited with cleaning up Times Square and he kept New York City and the country calm during the attacks of 9/11, earning him the nickname “America's Mayor.”

“That was the man meeting the moment,” says one interviewee in the spot.

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But Giuliani's need to stay in the spotlight ultimately proved to be his downfall as he hitched his wagon to President Donald Trump, taking on the role of Trump's personal attorney.

“A theme that runs through his life is that he's gotta be at the center of the action. Rudy's gotta be the star,” says a talking head.

In that role, Giuliani found himself supporting Trump's questionable dealings in Ukraine, which led to Trump's first impeachment, and potentially aiding and abetting insurrection on January 6, 2021 as a violent mob invaded the U.S. Capitol.

In its new documentary, Giuliani: What Happened to America's Mayor?, CNN explores the question of how Giuliani fell so far, working to showcase the complexities of a once respected man who became a polarizing political figure.

Giuliani: What Happened to America's Mayor? premieres Sunday, January 8 at 9 p.m. ET/PT on CNN.