Republican presidential candidate Donald Trump is reviving some of the ugliest political chapters of the 1990s with escalating personal attacks on Bill Clinton's character, part of a concerted effort to smother Hillary Clinton's campaign message with the weight of decades of controversy.

Trump's latest shot came Monday when he released an incendiary Instagram video that includes the voices of two women who accused the former president of sexual assault, underscoring the presumptive Republican nominee's willingness to go far beyond political norms in his attacks on his likely Democratic rival.

The real estate mogul has said in recent interviews that a range of Clinton-related controversies, including those that are unsubstantiated or widely discredited, will be at the center of his case against Hillary Clinton.

"They said things about me which were very nasty. And I don't want to play that game at all. I don't want to play it -- at all. But they said things about me that were very nasty," Trump said. "And, you know, as long as they do that, you know, I will play at whatever level I have to play at. I think I've proven that."

Clinton's campaign has largely refused to engage the recent attacks directly, instead focusing -- as Clinton did Monday during an appearance in Detroit -- on Trump's demeanor and job qualifications.

Clinton campaign spokesman Brian Fallon said Monday on Bloomberg TV that Trump's attacks were part of a "strategy to try to distract from an issues-based campaign, which is what we intend to run. . . . To me, every day he spends in this type of stuff is a misspent opportunity by him in terms of doing the outreach he needs to do to improve his numbers."

The race already appears to be teed up as a referendum on the two candidates' pasts rather than their visions for the country's future. Clinton has increasingly directed fire at Trump's long history of derogatory statements about women, his bankruptcies and other controversies to argue he is unfit for office.

Trump, meanwhile, has sought to brand the former secretary of state as "Crooked Hillary," pointing to such issues as the Whitewater real estate controversy in the 1990s and foreign donations to her family's philanthropic organization over the past decade. Trump also regularly accuses the Clintons of hypocrisy on women's issues and argues that Hillary Clinton has been an "enabler" of her husband's infidelities by attempting to discredit the women in question.

In one recent interview, Trump said another topic of potential concern is the suicide of former White House aide Vincent Foster, which remains the focus of intense and far-fetched conspiracy theories on the Internet.

"It's the one thing with her, whether it's Whitewater or whether it's Vince Foster or whether it's Benghazi. It's always a mess with Hillary," Trump said in the interview.

The real estate mogul and his allies hope that his tactics will bring fresh scrutiny to the Clintons' long record in public life, which conservatives characterize as defined by scandals that her allies view as witch hunts. Through social media and Trump's ability to garner unfiltered attention on the Internet and the airwaves, political strategists believe he could revitalize the controversies among voters who do not remember them well or are too young to have lived through them.

"The Clintons collectively have dodged many, many, many bullets. So much that was suppressed [by the media] is going to get re-analyzed. So many of the things that they slipped by on will get reexamined," Trump ally Roger Stone said Monday. "That's something they should have counted on before getting into the race."

At the same time, Trump has often dismissed scrutiny of his own behavior, including his questionable treatment of women, which served as tabloid fodder in New York City in the 1980s and 1990s. He has regularly criticized the media for reporting on events from decades ago.

"When was this? Twenty-five years ago? Wow, you mean you're going so low as to talk about something that took place 25 years ago," Trump said earlier this month when asked about pretending to be his own publicist in the 1990s.

The video that Trump published Monday on Instagram - and blasted out to his 8 million Twitter followers -- marked a stark turn in a campaign that has already been particularly nasty. The clip includes audio from two well-known accusers, Juanita Broaddrick and Kathleen Willey, describing their allegations against Bill Clinton, who is shown smoking a cigar. Then the video switches to a picture of Hillary Clinton and the sound of her laughing loudly, with the final words: "Is Hillary really protecting women?"

Broaddrick accused Bill Clinton of assaulting her in 1978, when she worked on his Arkansas gubernatorial campaign. Willey said the former president tried to kiss and grope her in a private hallway in the White House when he was president. Clinton has denied the allegations.

Democratic-aligned groups called Trump's attacks a distraction from his own record.

"Donald Trump is a known misogynist who tears down women for fun. His credibility among women is shrinking by the day, and playing 'gender card' politics isn't helping either," said Marcy Stech, vice president of communications at Emily's List. "It's these types of attacks that only draw more attention from Trump's extreme and hateful worldview toward women."

Rep. Peter T. King, R-N.Y., a Long Island moderate who voted against impeaching Bill Clinton in 1998, is skeptical of Trump's aggressive approach. He noted that House Republicans tried to run on similar issues in 1998 amid the impeachment debate and lost seats.

"We've been here before, and for most it's probably old news that people get a little squeamish about," King said in an interview. "Especially he brings it up in the abstract, he risks making the same mistake that Republicans made in 1998 when we got caught up in this stuff."

Stone said he expects a super PAC will air television ads and steer research to mainstream media organizations to revive elements of 1990s scandals. But he added, "What Trump is going to do only Trump knows. Trump is not scripted, he's not programmed and he's not handled, but he can read, and he does know the facts about the Clintons."

One issue on Trump's radar is the 1993 death of Foster, which has been ruled a suicide by law enforcement officials and a subsequent federal investigation. But some voices on the far right have long argued that the Clintons may have been involved in a conspiracy that led to Foster's death.

When asked in an interview last week about the Foster case, Trump dealt with it as he has with many edgy topics -- raising doubts about the official version of events even as he says he does not plan to talk about it on the campaign trail.

He called theories of possible foul play "very serious" and the circumstances of Foster's death "very fishy."

"He had intimate knowledge of what was going on," Trump said, speaking of Foster's relationship with the Clintons at the time. "He knew everything that was going on, and then all of a sudden he committed suicide."

He added, "I don't bring [Foster's death] up because I don't know enough to really discuss it. I will say there are people who continue to bring it up because they think it was absolutely a murder. I don't do that because I don't think it's fair."