Pollsters cannot cite a time when two presidential nominees have approached a debate holding such little public confidence in their propensity to tell the truth.

And there may be no modern precedent for the televised encounter of two American candidates creating an urgent new medium: The debate as lie detector.

For whatever pressure the debate moderator places on Donald Trump or Hillary Clinton to defend any misleading statements, misinformation or bald-faced lies Monday night, a phalanx of fact-checkers stand ready to pounce on the fibs of possibly the most heavily viewed presidential face-off of all time.

The results of a lie detector may be inadmissible in a court of law, yet in the court of public opinion a documented lie can be hazardous for any candidate. In the hardest-fought battleground states — such as Florida, where the average of polling portrays a dead-heat between Trump and Clinton — big lies can play poorly.

“If you tell a whopper, it’s a big chance it can make a difference, but if you tell a white lie, probably not,’’ says Susan MacManus, a professor of political science at the University of South Florida. She’s at the Long Island debate site to provide analysis for the ABC News affiliate in Tampa — Florida’s biggest media market, in a bellwether county that has voted the way Florida has since the 1960s.

A “whopper” could “push” undecided voters, MacManus says. “The people who can be pushed now in our state are the 20 percent or so who are independents, and if people are going to tune in they are going to tune into the first and last debates… Women are late deciders and so are young people, and for both groups ethics matters a lot.”

Most voters surveyed call Trump and Clinton not honest or untrustworthy — Clinton more so in the latest ABC News/Washington Post poll.

Debates seldom involve candidates who “lie, frankly, as frequently as Donald Trump does,’’ Clinton campaign manager Robby Mook said in dueling campaign interviews on ABC News’ “This Week.” And, just as Trump has called Clinton “a dangerous liar,” Trump manager Kellyanne Conway said, “You know, if you’re running against a Clinton, veracity is certainly always on the table.”

For many months, observers have cried “Pants on Fire” or assigned multiple “Pinocchios” to the questionable comments of candidates for president — piling many more such fouls on Trump than on Clinton. Yet, in the past couple of weeks, a piercing new word has entered the headlines of mainstream media: “Lie.”

If Clinton’s circuitous explanations about the confidential correspondence of her private email as secretary of state have provided critics with continual fodder for a case against her honesty, Trump’s prolonged denial of President Barack Obama’s birthright as an American citizen has proven as troublesome. Finally, though, his concession that Obama was born on American soil — and false assertion that the genesis of the “Birther’’ movement is traceable to Clinton — crossed a line in the minds of newspaper editors who by custom leave such judgement to columnists.

Introducing a New York Times podcast, “Is Lying Trump’s Strategy,” host Michael Barbaro stated: “The deception was so brazen, so demonstrably disprovable, that it felt like a milestone in campaign history: After relentlessly promoting the lie that Barack Obama was born outside the United States, Donald J. Trump looked into the cameras and declared that he had instead debunked that insidious myth.”

Dean Baquet, Times executive editor, started explaining inclusion of the word “lie” in headlines. “Politicians often exaggerate their records, obfuscate, say they did something great when it wasn’t so great,’’ he said on National Public Radio’s “Morning Edition” Sept. 22. “I think the moment for me was the birther story.”

“To say that that was a ‘falsehood’ wouldn’t have captured the duration of his claim, to be frank, the outrageousness of his claim,” Baquet said. “This was something else… If you look up ‘lie’ in the dictionary, it’s pretty clear. Actually it’s a synonym of falsehood. No, it would almost be illiterate to have not called the birther thing a lie.”

A couple days later, the headline, “A Week of Whoppers From Donald Trump” topped a story about a week of recent comments in which the writers counted “his 31 biggest whoppers, many uttered repeatedly. “All politicians bend the truth to fit their purposes, including Hillary Clinton,” Maggie Haberman and Alex Burns wrote. But Trump “has unleashed a blizzard of falsehoods, exaggerations and outright lies in the general election, peppering his speeches, interviews and Twitter posts with untruths so frequent that they can seem flighty or random — even compulsive.”

Among the examples repeated most often and certain to play in the first debate and days following it is Trump’s claim that he “was against going into the war in Iraq.” Haberman and Burns wrote: “This is not getting any truer with repetition.”

“You see what’s happening with my poll numbers with African-Americans. They’re going, like, high,” Trump said in North Carolina and Ohio last week, as polls show him winning “virtually no support” among African-Americans.

On the West Coast, the Los Angeles Times headline read: “Scope of Trump’s Falsehoods Unprecedented for a Modern Presidential Candidate.” Michael Finnegan wrote: “Never in modern presidential politics has a major candidate made false statements as routinely as Trump has. Over and over, independent researchers have examined what the Republican nominee says and concluded it was not the truth.” This included charges of “Pants on fire” by PolitiFact and “Four Pinocchios” assigned by The Washington Post’s Fact Checker.

Of course, both the New York and Los Angeles Times have since editorially endorsed Clinton. And some observers have questioned how much time PolitiFact devotes to scrutiny of Trump’s remarks versus analysis of Clinton’s comments.

“I’ve seen various media outlets trying to list the lies out there, and people have stopped counting,” MacManus says. “I love fact-checking, and I think it’s essential to hold people accountable. But what’s happened now is that the fact-checkers are viewed as rigged if it’s not the view you want.”

At the end of last year, PolitiFact, the website with a “Truth-O-Meter’’ sponsored by Florida’s Tampa Bay Times and other regional newspapers around the country, dubbed Trump’s campaign statements the “2015 Lie of the Year.”

This year, while rating most of Trump’s evaluated comments mostly false (44), false (89) or Pants on Fire (48), PolitiFact has counted few as true (11) or mostly true (29). The count on Clinton’s rated comments: 57 true, 71 mostly true, 57 half true, 37 mostly false, 27 false, six “Pants on Fire.”

Recent examples of pants-burners: Trump’s statements that, “Our African-American communities are absolutely in the worst shape they’ve ever been in before. Ever. Ever. Ever.” And that the number of undocumented immigrants in the U.S. “could be 34 million.”

Examples of Clinton’s offenses: “I am the only candidate who ran in either the Democratic or the Republican primary who said from the very beginning (that) I will not raise taxes on the middle class.” (PolitiFact found 15 who’d made the same pledge.) And on the investigation of her emails, FBI Director James Comey “said my answers were truthful, and what I’ve said is consistent with what I have told the American people.” (PolitiFact called this “cherry picking to the extreme.”)

In that Lie of the Year award, PolitiFact wrote: “Donald Trump doesn’t let facts slow him down. Bending the truth or being unhampered by accuracy is a strategy he has followed for years.”

This was the stage Clinton manager Mook was attempting to set for the first debate: “What we’re concerned about is that there might be some sort of double standard here,” he said. “You know, Donald Trump can’t lie on that debate stage and — and win or even get a passing grade.”

And on what was expected of debate moderator Lester Holt: “All that we’re asking is that, if Donald Trump lies, that it’s pointed out.”

Conway’s response: “I think they are really afraid that Hillary Clinton is just not a very good candidate. A majority of Americans don’t much like her and, according to your own poll, don’t trust her. Donald Trump is actually leading Hillary Clinton on the attribute of who is more honest and trustworthy in your own ABC poll.”

In that ABC/Post poll released Sunday — portraying a dead heat, Clinton with 46 percent support among likely voters, and Trump with 44, in a four-way contest— it’s clear that not only the campaign managers are questioning the candidates’ fidelity to the truth.

While just one-third of voters call Clinton honest and trustworthy, 62 percent say she’s not. More, 42 percent, consider Trump honest, while 53 percent say he’s not.

While the television networks armed with their own real-time fact-checking promote a debate potentially drawing 100 million viewers, eight in 10 voters surveyed did say they’d be watching this debate. And as Clinton and Trump and surrogates fan out across the country in the days following the show, an army of truth-squads will surely attempt to help them get their stories straight.