CHARLOTTE, N.C. — The closely-watched special U.S. House election being held here Tuesday is taking place in the shadow of a political scandal that, according to the candidates, is having a real impact on the race.

But this time around, the issue is not the illegal ballot harvesting that marred last year's contest, it's the fact the one of the candidates has been effectively running for over two years.

Democratic candidate Dan McCready likes to tell his supporters that he began running for the 9th Congressional District seat when his wife, Laura, was pregnant with their fourth child. Their daughter recently celebrated her second birthday.

The Republican candidate, state Sen. Dan Bishop, agrees, saying that McCready’s marathon campaign is why the race is by all accounts neck-and-neck in a district that President Donald Trump won by 12 points in 2016.

“The media sorta relentlessly asks me, ‘well why is this race close?’ And I have to remind them, Dan McCready has been running for 28 months,” Bishop told a small gathering of supporters recently at a refurbished barn in Union County outside of Charlotte.

McCready’s nearly two-and-a-half year campaign and Bishop’s late entrance into the race is the result of a mail-in absentee ballot scheme that led the North Carolina State Board of Elections to throw out the results of the 2018 election. After an investigation and a four-day trial, the board called for a new election.

Then-Republican candidate Mark Harris dropped his candidacy after admitting to misstatements during the emotional hearing. That led to a new primary election, which Bishop, a conservative state senator, won nearly four months ago.

The scandal of 2018, which occurred in the more rural parts of the district with fewer voters, is not in the forefront of this election. But the district’s history of absentee ballot fraud isn’t ignored either.

McCready mentioned it at a get-out-the-vote rally for supporters at the beer bar Brawley’s Beverage on this final weekend of the campaign — a subtle reminder that the fraud happened at the behest of Republicans.

“This election on September 10 is the people’s chance to get justice and have their vote heard,” McCready told NBC News.

Tuesday's election, which has become known as the "battle of the Dans," is being closely watched by national Democrats and Republicans to help gauge voters’ mood less than 14 months before the 2020 election.

McCready, a solar energy entrepreneur and former marine, is running as a moderate Democrat — "country over party" — in this district that hasn’t seen a Democrat in Congress since 1963. He’s squaring off against Bishop, who authored the controversial “bathroom bill” that prohibited transgender people from using the bathrooms and locker rooms of their gender identity.

Both campaigns are closely watching the early vote numbers, especially absentee ballots returned by mail. Both sides are also watching the vote data closely and are armed with lawyers on staff as well as volunteer lawyers in each of the eight counties to ensure a fair election.

Republicans and Democrats working with the campaigns as well as independent watchers say they have seen nothing abnormal in this election’s early vote or absentee ballot numbers.

The State Board of Election has mandated new forms to be used at the county boards of elections to track who requests absentee mail-in ballots and who submits them. They board also provides extensive detail on absentee ballots online and they have a team of investigators to follow up on complaints.

“If there’s an anomaly in the absentee ballot data, it will be found,” said Pat Gannon, spokesperson for the state Board of Elections.

Michael Bitzer, professor of southern politics at Catawba College in Salisbury, N.C., who tracks voter data in North Carolina elections, says that of all the early votes cast, fewer than three percent have been cast via mail, which he said is on par with the expected state average.

“I haven’t seen any kind of mysterious trends appear like exorbitant absnetee by-mail absentee ballot requests,” Bitzer said. “I just think 2018 brought such a spot light that everybody is on their best behavior.”

Still, the 2018 election is on the back of minds of voters. McCready supporter Mary Lou Cagle said that McCready should have declared the winner instead of calling for a new election that is likely to have lower voter turnout.

“I wish what they would have done is let Dan win,” she said. “I mean just throw those ballots out and let Dan win.” Bishop, who had nothing to do with the absentee ballot scandal, said he doesn’t think the Republican Party is tainted because of it, but he did acknowledge that some frustration among voters about holding a new election.

“I do think that people were very discouraged that 285,000 votes were cast aside on an issue that involved very very few,” Bishop told NBC News, referring to the amount of votes cast in the 2018 election.

Dan Bishop, the Republican candidate for senate in North Carolina's 9th District, speaks with supporters in Hope Mills on Aug. 10, 2019. Tom Williams / CQ-Roll Call file

In a tainted vote count, McCready was behind Republican Mark Harris in the 2018 race by fewer than 900 votes when Democrats swept congressional districts across the country.

Now that Democrats control the House of Representatives, political watchers are anxious to see how voters respond to Democrats in more conservative districts.

Bishop thinks it will give him an advantage. He told NBC News that voters “are seeing what the Democrats are all about,” pointing to the Green New Deal and some Democrats position to de-criminalize crossing the border. He is tying McCready to House Speaker Nancy Pelosi, Rep. Alexandria Ocasio-Cortez, and Sen. Elizabeth Warren.

McCready, meanwhile, has attempted to distance himself from national Democrats and instead run a campaign focused on health care, his biography and education, repurposing the playbook successfully deployed by scores of Democrats who won in 2018.

Bishop’s campaign is also working to put a dent into McCready, who has high name recognition after nearly 28 months on the campaign trail. McCready has built his image running biographical, positive television ads; Bishop has resorted to a mostly negative campaign in an attempt to shift public opinion of McCready.

Bishop told supporters that his campaign is working.

“We are surging. We’ve caught him and we’re going to beat him,” Bishop said to applause.

Bishop is also hanging on the president’s popularity in the district, insisting that Trump's support here remains “strong.”

Trump has been campaigning from afar for Bishop with tweets and emails to supporters. He’ll hold a Trump-style rally Monday night in Fayetteville and Vice President Mike Pence will host an event in Union County earlier in the day in an attempt to rally support to push Bishop over the finish line.