The hearing, which could prompt the North Carolina State Board of Elections to order a new vote in the district, may last until Wednesday and could include dozens of witnesses.

Congress, which has the constitutional authority to determine its membership, will be watching closely.

Here’s a guide to where things stand before Monday’s hearing.

There’s still an undecided election from the midterms?

The midterms — at least in the 9th District, which includes part of Charlotte and a vast, rural swath of southeastern North Carolina — have not ended, and a House seat that Republicans have held since 1963 is still at stake.

At first, it seemed the Republicans’ grip on the seat would continue: Mark Harris, the Republican nominee, took a 905-vote lead over his Democratic rival, Dan McCready. But state officials refused to certify Harris as the victor because of concerns about election fraud and, in particular, the conduct of L. McCrae Dowless Jr., a contractor for the Harris campaign.

What kind of fraud might have happened?

The principal concern involves absentee ballot harvesting — when a ballot is collected and mailed by someone who is not the voter or, in some instances, a close relative — and how Dowless and his associates may have relied on the tactic during their work for Harris. Although ballot harvesting is allowed in some states, it is illegal in North Carolina.

Allegations have also been raised about absentee ballot tampering and that elections officials in Bladen County, where absentee-by-mail statistics helped stir suspicions about fraud, may have aided Dowless.

Who is L. McCrae Dowless Jr.?

A prolific political operative in Bladen County, Dowless has long been a go-to contractor for Democratic and Republican candidates, especially in state and local races. He has also run for, and won, elected office himself, and his party loyalties have sometimes shifted. Over almost 15 years, according to state records, Dowless has gone from being a registered Democrat to unaffiliated to Democrat to unaffiliated to Republican.

He has a criminal record that includes convictions for perjury and insurance fraud, and he previously drew scrutiny, but not prosecution, for his political work. Harris acknowledged in December that, despite Dowless’ controversial history, he had directed his hiring as a contractor. But Harris maintained that he “had no reason to think that what he was doing was illegal.”

Dowless declined repeated requests for an interview with The New York Times and, through his lawyer, also refused to meet with state investigators. He could speak this week, though: Both the Harris and McCready campaigns identified him as a possible witness for the evidentiary hearing. He has not been charged with wrongdoing in connection to the 2018 election.

What’s the standard to trigger a new election?

North Carolina law gives the elections board the power to order a new vote if it finds that “irregularities or improprieties occurred to such an extent that they taint the results of the entire election and cast doubt on its fairness.”

But there is no firm guideline for when a disputed election meets that threshold. The state board has five members — three Democrats and two Republicans — and it takes four members to call a new election.

What does Mark Harris think should happen?

His position, like his opponent’s, is about what you would expect.

Harris’ campaign, in a brief to the elections board, argued that the state should certify the Republican nominee as the winner and that a new election would not be appropriate.

“Because the voter’s intent is key, any alleged ballot harvesting, standing alone, does not weigh in favor of a new election,” Harris’ lawyers wrote. “To be sure, absentee-by-mail ballot harvesting is illegal, and it should be referred to prosecutors for appropriate action.”

“But illegality in transmission is not necessarily indicative of invalidity of substance,” the campaign added. “Without evidence to show that the contents of ballots sufficient in number to change the outcome of the election were tampered with, any illegality in how they were delivered should be immaterial to the Board’s decision making.”

And what does Dan McCready want to happen?

In its own brief to the elections board, McCready’s campaign called for a new vote and accused Harris’ campaign of hiring Dowless because of his “proven history of generating a strikingly high, and downright suspicious, share of absentee-by-mail votes.”

“Though the full scope of fraudulent activity may never be known, the record makes clear that the results of the entire election are tainted, and its fairness is in doubt,” the McCready campaign wrote. “Moreover, the Harris campaign should have known it was benefiting from fraud, and there is strong evidence that they did know and that local election officials aided the scheme.”

Will there be criminal charges?

Maybe, but they will not be heard or adjudicated during this week’s elections board proceedings. The board can send any findings to prosecutors, some of whom have already been investigating irregularities, for possible charges.

Does the 9th District have a vote in the House right now?

No. Rep. Robert Pittenger, who lost a Republican primary to Harris in May, left power when the new Congress took office in early January, and the 9th District’s seat has been empty ever since. Although no House vote this year has been close enough that a single member’s decision would have changed the outcome, the 9th has been without representation as dozens of matters have gone before the House.

So when will Congress do something about all of this? Can it?

Under the Constitution, the House is “the judge of the elections, returns and qualifications of its own members,” and Congress could eventually determine that November’s balloting was compromised.

A formal refusal by Congress to seat a prospective member from the 9th District would lead to a new election, but it is unclear whether the House would take such a step if the state elections board certified a winner.