Intelligence community leaders and lawmakers of both parties have pleaded with political leaders to refrain from casting doubt on the legitimacy of the election, which they’ve emphasized could be amplified by foreign adversaries like Russia who seek to cast doubts about the legitimacy of American institutions.

Trump has ignored those warnings, repeatedly blaring unsupported suggestions that widespread mail-in voting will result in a fraudulent election.

“RIGGED 2020 ELECTION: MILLIONS OF MAIL-IN BALLOTS WILL BE PRINTED BY FOREIGN COUNTRIES, AND OTHERS,” Trump tweeted in June. “IT WILL BE THE SCANDAL OF OUR TIMES!”

He has echoed those warnings and reiterated them dozens of times in recent weeks, amid polls showing him trailing Democratic nominee Joe Biden.

But a senior FBI official on the same Wednesday call said any consequential election fraud is unlikely to materialize.

"We have not seen to date a coordinated national voter fraud effort during a major election,” the official said. “It's extraordinarily difficult to change a federal election outcome through this type of fraud alone.”

The comments from intel community leaders also contrast with Attorney General William Barr, who said last month that the expectation of a foreign incursion on mail-in balloting procedures is “common sense.”

“If you have wholesale mail-in voting it substantially increases the risk of fraud,” Barr said.

When asked by Rep. Mary Gay Scanlon (D-Pa.) if he had evidence to back up the claim that foreign adversaries could print fraudulent mail-in ballots, Barr replied, “I don’t, but I have common sense.”

Scanlon called the claim “disinformation,” to which Barr shot back, “It’s not disinformation.” But when he sought to elaborate, Scanlon cut him off and changed the subject.

More broadly, the national security officials issued reassurances about the level of visibility and awareness they have into foreign election threats this time around — as opposed to in 2016, when intelligence officials were caught off guard by the ferocity and breadth of Russia’s interference campaign.

“We are way ahead of where we were in 2016,” said a senior official at DHS’ Cybersecurity and Infrastructure Security Agency. The landscape is more promising, too, the official said, with no obvious “ramp-up in activity targeting election infrastructure” that officials were seeing from the Russians around this time four years ago.

Still, the country’s top counterintelligence official Bill Evanina has issued two warnings in recent weeks about ongoing malign influence campaigns by Russia, China and Iran that could influence the election. The most recent statement detailed Russia’s attempts to undermine Democratic presidential nominee Joe Biden, while pointing to rhetoric by China and Iran that has been critical of the Trump administration and the U.S. more broadly.

Trump has since seized upon the assessment about China’s political activities to suggest that Beijing wants Biden “to win,” which the intelligence community has not stated publicly or offered evidence for. Director of National Intelligence John Ratcliffe released his own statement last week indicating that China poses the greatest threat to U.S. national security, including election security.

“China poses a greater national security threat to the U.S. than any other nation – economically, militarily and technologically. That includes threats of election influence and interference,” Ratcliffe has said in a statement, initially sent to conservative outlets Fox News and the Washington Examiner in the last week.

Intelligence officials on Wednesday described China, Russia and Iran as the “big three,” with one FBI official calling them all significant purveyors of malign influence activity. But asked whether China in particular is trying to help Biden win, the ODNI official referred back to the most recent statement issued about the three countries’ efforts.

Democrats, though, including Speaker Nancy Pelosi and Senate Democratic Leader Chuck Schumer, have accused Evanina of drawing a false equivalence between the three countries when intelligence indicates that only Russia is taking specific steps interfering in the 2020 election.

ODNI officials said Ratcliffe's statement is consistent with Evanina's earlier pronouncements and echoes other statements by intelligence community leaders about the long-term threat China poses to the United states.

Tim Starks contributed reporting for this story.