What will Lester Holt do when Donald Trump says that he opposed the Iraq war from the beginning?

Holt, 57, the most-watched daily news broadcaster in the country, has been tapped to moderate the first presidential debate Monday between Trump and Hillary Clinton. To say there is a lot riding on the night is not quite to capture it.

A record 100m Americans are expected to watch the showdown, probably making it one of the biggest television broadcasts ever. The political stakes are higher: many partisans on both sides think the fate of the republic, all 330m strong, is on the line.

Although under intense pressure from the Democratic side to play fact-checker as a bulwark against Trump’s baloney, and under equal pressure from the Republican side to stay out of it, Holt has not talked about how he sees his role. But he has shown persistence, in exclusive interviews with both candidates in recent months, in pinning the candidates down where they would rather speak unaccountably.

Hillary Clinton supporters hope that means that Holt might intervene, unlike his network colleague Matt Lauer at a forum earlier this month, should Trump repeat his lie about having opposed the Iraq invasion from the beginning, or should Trump roll out any of the other 48 “pants-on-fire” lies that the nonpartisan group Politifact has counted him telling.

Trump supporters may hope that a different Holt shows up, one closer to the amiable broadcaster who co-hosted a weekend morning show for 12 years. They want the man who announced the Westminster Kennel Club dog show for three consecutive years in the aughts, not a fact-checker of the nightly news.

After 35 years as a newscaster, Holt currently hosts the top-rated nightly news program in America, NBC Nightly News, attracting 7 to 8 million viewers on an average weeknight. Any doubts about the calibre of his talent that accompanied his unusual arrival in the role – amid the career implosion of his predecessor, Brian Williams – quickly dissipated. Holt drove the ratings still higher.

A native Californian who has written that he “grew up on air force bases”, Holt has reported from zones of armed conflict and natural disaster while charismatically serving up lighter stories as weekend anchor of NBC’s morning news and variety show, Today. He also plays upright bass.

Holt will encounter an unprecedented challenge, however, on Monday night, when he will mediate between two hungry candidates now tantalizingly close to claiming the most powerful post on Earth. He has interviewed both candidates in recent months, and brought a healthy journalistic antagonism to the job.

In June, Holt sat three feet away from Trump on gaudy Louis XVI chairs in Trump Tower, nearly knee-to-knee, and demanded that the candidate show evidence for a recent claim that Clinton’s private email server had been hacked. Anyone who doubts Holt’s ability to fact-check Trump should watch the exchange, in which he reduces Trump to the lame assurance, “I will report back to you.”

Two weeks later, Holt pressed Clinton on the opposite side of the email issue, confronting her with a finding by FBI director James Comey that she had been “extremely careless” in handling classified information. She ended up squirming, too.

Trump has expressed displeasure with Holt. “Lester is a Democrat,” Trump flatly told Fox News a week ago. But whether Holt checks that “fact” at the debate or not, it is false. Holt is a registered Republican.

