Depressed and drinking to excess after the failure of his run for the Republican presidential nomination in 2008, Rudy Giuliani secretly recovered at the Florida home of a close friend and ally – Donald Trump.

“We moved into Mar-a-Lago and Donald kept our secret,” Giuliani’s third wife, Judith Giuliani, says in a new book.

Giuliani: The Rise and Tragic Fall of America’s Mayor, by Andrew Kirtzman, will be published in September. The Guardian obtained a copy.

In 2018, Giuliani told the New York Times he “spent a month at Mar-a-Lago, relaxing” after the primary a decade before. He has not otherwise discussed the period.

Giuliani initially polled well in 2008 but won just one delegate and dropped out after placing fourth in Florida.

The former mayor, Kirtzman writes, had “dreamed of becoming president from a young age, [but] blew his big moment when it arrived”.

Judith Giuliani tells Kirtzman her husband fell into “what, I knew as a nurse, was a clinical depression”.

“She said he started to drink more heavily,” Kirtzman writes. “While Giuliani was always fond of drinking scotch with his cigars while holding court at the Grand Havana or Club Mac, his friends never considered him a problem drinker. Judith felt he was drinking to dull the pain.”

Giuliani has repeatedly denied having a drinking problem. But reports of his drinking while fulfilling his late-career role as Trump’s personal attorney are legion, whether regarding his behavior around reporters or in his presence at the White House on election night in 2020, when he exhorted Trump to declare victory before all results were counted.

In testimony to the House January 6 committee, Jason Miller, a senior Trump adviser, said Giuliani was “definitely intoxicated” that night.

Kirtzman’s reporting of Giuliani’s little-known 2008 stay at Mar-a-Lago – a period when in Giuliani’s ex-wife’s words he was both speaking to therapists and “always falling shitfaced somewhere” – also prefigures Giuliani’s current role in American public life, as a chaotic, picaresque Trump booster seemingly impervious to personal or political embarrassment.

Trump is a lifelong teetotaler but also a longtime Giuliani ally. In 2008, Kirtzman says, as Giuliani was struggling even to get out of bed, Trump came to his rescue.

The former mayor and his wife, Kirtzman writes, moved into a bungalow across the street from Mar-a-Lago but connected by a tunnel underneath South Ocean Boulevard, one of many little known passages and rooms beneath the expansive resort. The secret route allowed the couple to come and go from Trump’s home without the media knowing.

As Kirtzman’s book nears publication, underground rooms at Mar-a-Lago are in the news, after the FBI searched some for classified material taken from the White House at the end of Trump’s four years as president.

Giuliani eventually emerged from seclusion to appear on Saturday Night Live. He made “self-deprecating jokes about the failure of his campaign”, Kirtzman writes, but “his makeup barely hid a large scar above his right eyebrow”. According to Judith Giuliani, the scar was the result of a fall when getting out of a car.

Kirtzman writes that Giuliani’s third wife “was known to exaggerate, and the depth of his depression [during his secret spell at Mar-a-Lago] is something that only she and Giuliani knew for certain”. But the author also quotes friends, among them the 2013 Republican New York mayoral candidate Joe Lhota, as saying the Giulianis were out of touch at the time in question.

Kirtzman recounts Giuliani’s career from his days as a hard-charging New York prosecutor to two terms as a controversial mayor, the 9/11 attacks and Giuliani’s widely praised leadership in the immediate aftermath.

The author also covers Giuliani’s business deals after leaving office and his failed Senate run against Hillary Clinton in 2000.

In Giuliani’s meltdown after the primary in 2008, Kirtzman finds the seeds of a relationship which ultimately saw Giuliani contribute to Trump’s first impeachment, over approaches to Ukraine for political dirt, and to Trump’s attempts to overturn the 2020 election. Those efforts resulted in Trump’s second impeachment, over the Capitol riot, and extensive professional and legal jeopardy for Giuliani.

As reported by the New York Times, Kirtzman ultimately describes a Giuliani associate’s failed request that Trump pardon his ally in the aftermath of the Capitol attack – and give him the Presidential Medal of Freedom while he was at it.

Giuliani and Trump had “a compelling kinship”, Kirtzman writes. “The former mayor and the famous developer were two New York colossuses, dinosaurs from another time and place.” Judith Giuliani tells Kirtzman Trump and his own third wife, Melania Trump, “kept a protective eye” on their friends.

Judith, Kirtzman writes, “contends that, eight years before Washington began talking about Rudy Giuliani and Donald Trump in the same breath, the future president took the failed candidate under his protective wing at a vulnerable moment.

“What’s clear is the two men’s friendship survived when a hundred other Trump relationships died away like so many marriages of convenience. Giuliani would never turn his back on Trump, much to his detriment.”