Veteran campaign reporters are calling on media outlets to sharply increase their fact-checking of presumptive Republican presidential nominee Donald Trump, telling Media Matters “the stakes are too high” to let Trump get away with peddling conspiracy theories and near-constant falsehoods.

In the week since Trump’s win in the Indiana presidential primary essentially clinched the nomination for him, the candidate has faced criticism from media critics and fact-checkers for his continued embrace of outlandish conspiracy theories. CNN’s Brian Stelter on Sunday called on journalists to confront Trump “head-on” over his misinformation. Washington Post fact checker Glenn Kessler hit a similar note in a May 7 article, writing that outlets have “no excuse” to let Trump get away with falsehoods.

In conversations with Media Matters, Kessler and several veteran presidential campaign reporters highlighted the sheer tonnage of misinformation from Trump, with several arguing that outlets need to be more aggressive when challenging the Republican.

“The Trump lies are so many and they come out at such a rapid fire, Gatling-gun fashion, it is hard for the reporters to keep up in May. I can just imagine what it will be like in October,” said Walter Shapiro, who covered nine presidential campaigns dating back to 1980 for The Washington Post, Newsweek, Salon and others. “The most important thing is that you don’t put the fact checks in some separate envelope done by the fact-check expert. You have to put as many fact checks as you can in the story of the speech, in the story of the assertion and if necessary don’t resort to euphemisms, like ‘misspoke.’ He did not misspeak, he did not obfuscate, he did not miss the meaning -- he lied.”

Trump’s falsehoods and conspiracies have piled up over the course of the campaign, running the gamut from his repeated (and often unchallenged) boast that he opposed the Iraq War from the beginning to more bizarre claims like his recent embrace of a National Enquirer conspiracy linking Sen. Ted Cruz’s father to JFK assassin Lee Harvey Oswald.

“These are totally different problems than we have ever faced before,” Shapiro said about covering Trump. “I give lots of news organization in the months ahead a lot of latitude because we have never dealt with someone for whom truth is as dispensable as Kleenex in politics.”

He said part of the problem is when news outlets carry Trump speeches and rallies live, which by nature prevents immediate fact-checking.

“The problem is if the networks are going to give you one hour of unedited access a night, there is no way for the fact checks to catch up,” he said. “There are dictators who control the media who have less access than he does.”

David Yepsen, a former top political reporter for the Des Moines Register for 34 years, said news outlets need to “double-down on fact-checking” as the campaign continues.

“News organizations can take each one of these statements apart,” Yepsen said via email. “They can't be blown off or dismissed. The tone has to be calm, factual, but dispassionate and methodical. Reporters need to keep the focus on Trump and his statements.”

He later added, “It is also going to be critically important to get this debate out on social media. It's more important than a lot of reporters want to admit because more and more people are getting information about the campaign in this way.”

Adam Clymer, a former New York Times campaign reporter from 1977 to 2003, said the lack of scrutiny in the past is due to time pressures and poor editing, but that cannot continue.

Asked how journalists can counter him going forward, Clymer said, “By repeating after every time he says it that ‘Mr. Trump has offered no evidence of his theory that has been debunked by X, Y, or Z.’”

“Somebody’s got to be responsible,” Clymer urged. “Everything about his substance becomes more important when someone may be the nominee.”

He added, “Since Trump makes more stuff up than most people, he becomes a particularly glaring example of the press’ shortcomings. Do the basic job, which is different than what they have been. But it is not just reporters, don’t let editors off the hook at all levels.”

“He is off the charts,” said Kessler, who writes The Fact Checker column for The Washington Post.

Of the 34 fact-checks done on Trump in the column, nearly 70 percent have resulted in four Pinocchios, which is the site’s worst rating, Kessler said. “Your average politician gets 10 percent to 20 percent of their ratings as four Pinocchios.”

At PolitiFact.com, the Pulitzer Prize-winning fact-checking site, 62 percent of Trump comments that were reviewed received either False or “Pants on Fire,” its worst rating.

Angie Holan, PolitiFact editor, says no other 2016 presidential candidate even comes close.

“The results are the results, he’s wrong pretty regularly,” she said. “He gets small details wrong, too. He said the trade deficit with China is $500 billion. It’s not, it’s $300 billion. That’s quite a bit to be wrong. You add up wrong on big things and wrong on little things and that’s how he gets such a bad record.”

Kessler agreed the answer is for reporters to increase their scrutiny as they would any unreliable source.

“He says this stuff and keeps saying it,” Kessler said. “There is little excuse for not saying something to him when, for instance, he says he was against the war in Iraq or that Hillary Clinton started the birther movement -- things that have been fact-checked and found to be bogus.”

And Trump’s falsehoods are nothing new, according to people who covered him in the 1980s when he was a rising real estate mogul and New York gossip page regular.

Among those was Susan Mulcahy, former editor of the New York Post’s Page Six from 1983 to 1985. She recently penned a piece for Politico recounting his history of lies.

Her advice to today’s campaign reporters who must cover him through Election Day: “Every statement that he makes has to be checked. Even mundane, innocuous things.”

She suggested treating him as a lawyer would a witness on the stand, saying “be prepared for answers to some of the questions ahead of time,” later adding that lying “doesn’t bother him, he has been doing this for so long.”

Walter Mears, a Pulitzer Prize-winning former Associated Press campaign reporter, said the challenge is for journalists to scrutinize him more than most candidates because of his poor factual record.

“It requires more homework covering a guy like this, and the trouble with Trump is you never know what he is going to make up next,” Mears said. “It is not argumentative to say that Trump is lying, it is not argumentative if you state the actual fact.”

Clark Hoyt, a former reporter and editor for Knight Ridder and McClatchy -- who covered presidential races in 1968, 1972, and 1976 -- said Trump’s level of dishonesty is unprecedented in American politics and requires a demand for truth.

“If he says something that is demonstrably false it should immediately be called that. We have an obligation to even point out the history of these things, that this has been a pattern with Trump and not to let readers or viewers forget it. The stakes are too high,” said Hoyt, also a former public editor for The New York Times. “You have to be prepared to say what he says and then say what the truth is. That puts a great burden on news organizations to be really fast on their feet with research and the resources to dig into some of these things.”

Al Tompkins, a senior faculty member at The Poynter Institute, said reporters need to stick to the basics and not let lies pass by unchecked.

“He does seem to say a lot of things that just simply are not true,” said Tompkins. “He has a very high negative and part of that negative seems to be his demeanor, but also whether or not he can be trusted.”

Media Matters recently highlighted several other examples of journalism experts and veteran reporters calling on the media to fact-check Trump more effectively: