Donald J. Trump and Bill Clinton used to be golfing buddies and occasional telephone friends. Trump donated to the former president’s charitable foundation. Clinton attended the billionaire developer’s lavish third wedding in 2005.

But as Trump, the Republican presidential candidate who is leading most polls, sets his sights on a potential general election matchup against Hillary Clinton, he is making her husband’s history of marital infidelity a central issue. On Monday, Trump accused Bill Clinton of having a “terrible record of women abuse” and warned that he would be a liability to her campaign.

The assault on Clinton’s character has been couched as a counterpunch. Hillary Clinton said last week that Trump had a “penchant for sexism” after he said that she was doing “disgusting” things in the bathroom during the last Democratic presidential debate.

Over the weekend, Trump said that that Hillary Clinton was playing the “woman’s card” and that her husband’s sexual history would be fair game as the 2016 race ramped up. ”His presidency was really considered to be very troubled, to put it mildly, because of all of the things that’s she talking to me about,” Trump said Sunday on Fox News.

Bill Clinton admitted to having an affair with an intern while he was president and rumors that there were other instances of infidelity have swirled around him for years. His political opponents tried unsuccessfully to have him removed from office and the issue has largely receded in the ensuing decades.

But Trump is going there.

In pursuing this line of attack, Trump appears to be taking a page from the playbook of his former political adviser Roger Stone. Stone, a veteran Republican strategist who worked for Richard Nixon and Ronald Reagan, published a book earlier this year titled “The Clintons’ War on Women” in which he accuses Bill Clinton of being a serial philanderer and a rapist who he compared to the disgraced comedian Bill Cosby.

Although Stone is no longer officially affiliated with Trump’s campaign, he has been encouraging the criticism of Bill Clinton on social media while promoting his book. He accused Hillary Clinton on Monday of bullying her husband’s sexual assault victims and over the weekend he reposted an old photograph on Twitter of Bill Clinton and Monica Lewinsky standing together in the White House.

The Clintons have publicly moved past their marital problems and efforts to dredge them up could backfire against Trump since voters tend to view Hillary Clinton sympathetically whenever the issue has come up.

The strategy also represents another about-face for Trump, who has been friendly with Bill Clinton over the years and even called him before announcing his presidential bid in May.

In 2008, Trump suggested during an interview that Clinton’s infidelity was no big deal.

“Look at the trouble Bill Clinton got into with something that was totally unimportant,” Trump said on CNN. “And they tried to impeach him, which was nonsense.”

Bill Clinton has also praised Trump as recently as September, when he said the Republican had a lot of “pizzazz and zip.”

He was more glowing four years ago even when asked about Trump’s promotion of the myth that President Barack Obama was not really an American citizen.

“Donald Trump has been uncommonly nice to Hillary and me,” Bill Clinton said as he dismissed the birther controversy as nonsense. “We’re all New Yorkers. And I love playing golf with him.”

© 2015 The New York Times Company