Midway through the nearly hourlong debate, Tim Russert, the host of “Meet the Press” and the evening’s moderator, looked up from his notes at Hillary Clinton, the first lady-turned-Senate aspirant from New York, standing across the stage.

“The issue of trust and character has been raised repeatedly in this campaign,” he began, dutifully building the tension inside the room. As Russert finished his preamble, a video began to play, showing an interview Clinton gave two years prior in which she lashed out those who’d accused her husband of having an affair in the White House.

Did Clinton regret “misleading the American people,” Russert wanted to know, before asking if she should apologize to those she’d labeled right-wing conspiracy theorists.

Clinton, who had watched along, nodded gently and took a breath. A strained look came to her face. Her eyes moved away from Russert as she began speaking in measured, almost pained tones.

“Well, you know, Tim, that was a very, a very painful time for me, for my family and for our country,” she said. “It is something that I regret deeply that anyone had to go through.”

As she explained that she lacked the perspective from which to properly judge the entire sordid episode, her shoulders shrugged. Occasionally, she glanced back to Russert. But her gaze, by and large, remained downward and her hands moved little.

“Obviously I didn’t mislead anyone,” she went on. “I didn’t know the truth. And there’s a great deal of pain associated with that, and my husband has certainly acknowledged that and made it clear that he did mislead the country as well as his family.’’

It was an uneasy, fascinating moment, one that The New York Times described as “the most striking” of the evening. But what came next was equally compelling. Russert turned to Rick Lazio, Clinton’s opponent in that race, and read him a past comment in which Lazio said Clinton had “embarrassed” the country.

Lazio seemed even less certain than his opponent. As he begins to speak, he fidgeted ― his body swaying left and right. His eyes never looked at Clinton even as he ostensibly addressed her.

“I think that, frankly, what’s so troubling here, with respect to what my opponent just said, is somehow that it only matters what you say when you get caught,’’ he replied, a few “uhs” peppering his words. “And character and trust is about, well, more than that.”

That moment, in that debate, on that night in mid September 2000 was the most direct challenge an electoral opponent has ever made to Hillary Clinton about her husband’s infidelities.

Until now.

Over the past few days, Donald Trump’s campaign has launched a sub rosa attack on Bill Clinton’s affairs by praising its own restraint in not bringing the matter up. On Friday, however, Trump removed any lingering doubt that he would aggressively and directly prosecute the issue. In an interview with The Times, he called Hillary Clinton an “enabler” of “the single greatest abuser of women in the history of politics.” For a warning shot, he added this dark coda: “She’s nasty, but I can be nastier than she ever can be.”

While the Clinton campaign has so far responded with nonchalance, Republicans outside Trump’s orbit seem practically appalled by the prospect. Both they and Clinton’s team are old enough to recall what happens when ― as with that Lazio debate ― Bill’s peccadilloes are turned into campaign grist.

“Any number of Republicans have cautioned against Donald Trump taking this low road,” said Brian Fallon, Clinton’s press secretary. “It seems like it is not at all a considered strategy that they are adopting, but rather an impulsive move by Donald Trump that has become their strategy by default… It will backfire on him.”

ASSOCIATED PRESS Donald Trump has hinted he will go after Bill Clinton's infidelities in the next presidential debate.

Months before Russert raised the question during that debate, Republicans hoping to block the former first lady from capturing a New York Senate seat had reached a similar conclusion as Fallon. Then-New York City Mayor Rudy Giuliani had flirted with making a Senate run of his own. And his aides convened a voter focus group to test out prospective issues and lines of attack.

Longtime GOP operative Rick Wilson had another veteran Republican hand ― Frank Luntz ― conduct the group. As Wilson recalls, women took the attacks against Bill as “totally out of bounds.” It wasn’t just Democrats, but Republicans too.

“It was a totally ineffective attack in moving voters to Rudy, even if they weren’t pissed off and offended,” Wilson emailed. “It made [Clinton] more likable and we even had people saying things like, ‘Well, she deserves to be a Senator after how badly Bill treated her.’”

The responses could hardly have been mind-blowing. During Bill Clinton’s impeachment hearings, Hillary Clinton’s favorability ratings had skyrocketed. She was the most admired woman in Gallup’s 1998 poll, with a number that had doubled from the previous year and dwarfed second-place finisher Oprah (28 percent to 8 percent).

Still, the Luntz focus group was a bright red flag that the Clinton marriage, and all its complications, was not to be broached in the electoral arena. While Giuliani ultimately passed on making a run, Lazio largely followed that advice.

After his campaign sent out a fundraising letter accusing the Clintons of having “embarrassed our country and disgraced their powerful posts,” he refused to elaborate on what specific embarrassment he was citing. When Clinton was questioned by the press about the Lewinsky affair and the impeachment trial, his campaign remained quiet. And when Kathleen Willey, a former White House aide who claimed Bill Clinton sexually assaulted her, announced that she was ready to help Lazio’s campaign, his aides sought distance.

“This campaign is going to be about New York’s future and not the Clintons’ past,” a Lazio spokesperson said.

Lazio was forced to address the topic when Russert brought it up. But even then, he walked on eggshells.

“I steered away from making a point of any of those scandals during my debate and sidestepped reacting to or amplifying Tim Russert’s question,” he recalled in an email to The Huffington Post. “I was convinced then as I am now that public character was the salient issue, rather than what happened in Hillary Clinton’s marriage.”

ASSOCIATED PRESS The more memorable moment from the 2000 Senate debate.

That 2000 debate would ultimately be remembered for a separate exchange that evening ― one where Lazio appeared to violate Clinton’s personal space by walking over to her lectern and demanding she sign a pledge to get outside money out of their election. The issue of the Clintons’ marriage never again rose, recalled Howard Wolfson, a spokesman for her Senate campaign. Nor did it come up when she ran against Barack Obama in the 2008 Democratic primary, recalled Phil Singer, a spokesman for that campaign.

By the time the 2016 election rolled around, many Republicans seemed convinced that dredging up the matter was as pointless as it was counterproductive. Katie Packard, a top GOP consultant, practically begged the candidates to avoid doing it. “Republicans have an opportunity” to win over independent women and even some Democratic women voters, she emailed HuffPost in late December. “But the one thing that causes them to come to her defense is when she is attacked for what they perceive as Bill’s moral failings. Whether they relate, or they just feel it’s unfair, they defend her.”

Even those who had fought the issue on the front lines sought to keep it in the past. “It’s been litigated,” former congressman Asa Hutchinson, who had helped lead the impeachment hearings in 1998, told Time magazine. “It was litigated, the judgement was made by the United States Senate, and I think we need to move on from that.”

For months, Trump ― a candidate with a proclivity for slinging mud but one with a complicated marital history of his own ― appeared to agree. But his poor performance in the first debate and the precarious electoral position he finds himself in has apparently altered his calculus.

Not everyone is convinced the strategy will backfire. In a twist, Giuliani, who commissioned that 2000 Luntz focus group, has been egging him on. And even Lazio argued that to attack Clinton for her husband’s infidelity is fundamentally different than to take issue with the way she maligned “the character of the women who might have been involved with her husband.”

But the number crunchers and image gurus in the party are notably nervous. As Trump makes his 11th-hour gambit, they see shades of that 2000 debate moment.

“Trump looks mean when he goes after Bill Clinton,” said Luntz. “Voters think it’s inappropriate and he is not telling anyone anything they don’t know. He’s not being informative. He’s just being accusatory. There are so many great issues to challenge her on this isn’t one of them. It will create a sympathy for her that does not exist.”

J.M. Rieger contributed reporting.