For years, President Bill Clinton was the best friend Donald Trump always hoped to have.
When scandal engulfed Clinton's White House, Trump leapt to the president's defense. "He's probably got the toughest skin I've ever seen and I think he's a terrific guy," Trump told CNN.
Then there were Trump's pitches to the former president to settle in a gilded Trump building in Manhattan when he and Hillary Clinton left the White House. They moved to Westchester instead. His overtures for them to vacation at his Mar-a-Lago estate in Palm Beach were also rebuffed. The Clintons preferred the Dominican Republic.
When Clinton had trouble joining a conservative Westchester golf club, Trump boasted that he welcomed the former president to a newly built Trump National Golf Club, a five-minute drive from the Clintons' Chappaqua, N.Y., home.
"He's a great gentleman, a good golfer and a wonderful guy," the real estate developer said of Clinton, who, in reality, is a so-so golfer known for taking mulligans.
In the past week, any semblance of a friendship between Trump and Bill Clinton came to an ugly end as the former president and his wife's presidential campaign found themselves in a muddy battle over sexism with the Republican candidate who has upended this election cycle with his insults and attacks.
"If Hillary thinks she can unleash her husband, with his terrible record of women abuse, while playing the women's card on me, she's wrong!" Trump wrote on Twitter on Monday.
The criticism of Bill Clinton's personal life comes as Hillary Clinton is increasingly relying on the former president, mentioning him in almost every speech as she praises his economic record. But Trump's attacks on him are now rippling through the race, with other candidates and even a prominent newspaper columnist suggesting that Bill Clinton's sexual history is fair game.
"This works for Trump because it reinforces what his most ardent supporters believe to be his greatest strength," said Kevin Madden, a Republican communications strategist. "He will say things that no one else will say but that need to be said."
On Monday, Bill Clinton will oversee two organizing events for Hillary Clinton in New Hampshire — his first solo outing on the campaign trail in a state where he remains widely popular and where polls show Hillary Clinton slightly trailing Sen. Bernie Sanders of Vermont.
Trump's turn against the former president started last week when Hillary Clinton, in response to Trump's use of a crude sexual reference to describe her loss to Barack Obama in 2008, accused him of having a "penchant for sexism."
On Saturday, Trump said on Twitter: "Hillary Clinton has announced that she is letting her husband out to campaign but HE'S DEMONSTRATED A PENCHANT FOR SEXISM, so inappropriate!"
He went further on Tuesday, saying that in Bill Clinton's political career, "there were certainly a lot of abuse of women, and you look at whether it's Monica Lewinsky or Paula Jones or many of them."
In response to Trump's latest onslaught, Hillary Clinton's campaign said in a statement that "Hillary Clinton won't be bullied" or "distracted by the slings he throws at her and former President Clinton." A spokesman for Bill Clinton declined to comment.
Trump's tactics could backfire. Hillary Clinton had some of her highest approval ratings ever after revelations that Bill Clinton had a relationship with Lewinsky, a 22-year-old White House intern.
This month at a New Hampshire town hall, a young woman asked Hillary Clinton about several women who alleged they were sexually harassed by Bill Clinton.
"You say that all rape victims should be believed," the woman said. "Should we believe them as well?"
Hillary Clinton did not hesitate. "Well, I would say that everybody should be believed at first until they are disbelieved based on evidence," she said, with an awkward smile, as the crowd applauded.
Still, the issue seems to be echoing, at least among her detractors. Other Republican candidates, including Carly Fiorina and Ben Carson, have followed Trump's lead, saying Bill Clinton's history is a legitimate criticism, though Fiorina said she doubted voters would care. Bill Clinton, after all, is 69 years old and the Lewinsky scandal happened nearly two decades ago.
Washington Post columnist Ruth Marcus has been critical of Trump but on Tuesday wrote that she agreed with him that Bill Clinton's past is relevant to his wife's campaign, given that she is simultaneously utilizing her husband and calling Trump sexist.
"These moves open a dangerous door," Marcus wrote. "It should surprise no one that Trump has barged right through it."
Trump has been the most direct in his attacks on Bill Clinton, but Republicans, concerned about the party's declining appeal to women, have long considered using the former president's personal life and Hillary Clinton's response to the women who alleged extramarital affairs.
Stuart Stevens, a Republican operative and Mitt Romney's chief strategist in his 2012 campaign, said the way the Clinton operation disparaged women who complained about the president's behavior in the 1990s "would be all but disqualifying in a Democratic primary" nowadays.
During Bill Clinton's 1992 campaign, Betsey Wright, a close aide, coined the term "bimbo eruptions" in describing women alleging extramarital affairs against the president. According to White House-era documents from Diane D. Blair, a close friend of Hillary Clinton's who died in 2000, the first lady had referred to Lewinsky as "a narcissistic looney toon."
Until last week, Trump had hardly uttered a negative word about Bill Clinton. At the time, he said the president had been treated unfairly for his relationship with Lewinsky.
Trump has been a donor to the Bill, Hillary & Chelsea Clinton Foundation and to Hillary Clinton's Senate campaign. While a senator from New York, Hillary Clinton and her husband attended Trump's 2005 wedding to his third wife, Slovenian model Melania Knauss, held in a $42 million ballroom at his Mar-a-Lago estate decorated to resemble Versailles. (the Trumps were not invited to Chelsea Clinton's 2010 wedding.)
"He liked them and their star quality, and he respected a lot of things Bill Clinton did as president," said Edward G. Rendell, a former governor of Pennsylvania who is close to the Clintons. "That's all out the window now," he added.
In an email, Trump said his friendship with Bill Clinton was strictly for business reasons. "It was my obligation to get along with all politicians," he wrote. "And I did it better than anybody."
He said he did not recall whether the Clintons had stayed at Mar-a-Lago in Palm Beach. "If they did want to stay there, or stayed there, it only shows that they have good taste," he added.
Some have suggested that Trump, whose own affair with Marla Maples and his split from his first wife, Ivana Trump, were splashed across tabloids, is an imperfect messenger on the issue of fidelity.
Trump also opens himself up to criticism about his own personal life, including allegations that he assaulted Ivana Trump, which he has denied and which the former Mrs. Trump recently backed away from.
Trump, however, said he was "the perfect messenger because I fully understand life and all its wrinkles," and reiterated his claim that Hillary Clinton had bullied some of the women who accused her husband of improprieties.
Republican opponents have highlighted Trump's previously fawning comments about Bill Clinton. Back in 1999, Trump expressed admiration for Bill Clinton's retail political skills, telling CNBC in 1999, "I wish I could be like that. I can't."
And a few years later, he echoed that comment, recalling an anecdote about watching Bill Clinton work a crowd.
"He shook hands with everybody out there," Trump said. "And some of these people had filthy hands."