The North Carolina 9th District seat has remained vacant for a third of the 116th Congress — the fallout from a brazen case of election fraud that may have affected the outcome of the 2018 election. Allegedly, a consultant for Republican candidate Mark Harris coordinated an effort to illegally collect unsealed absentee ballots, mislead election authorities and, in some cases, fill out ballots on behalf of voters. As a result, the North Carolina State Board of Elections voted in February to redo the congressional race and later set a new election for Sept. 10. Now, the 9th District will finally vote on a new representative in an election that could go either way. Here’s a look at what’s already happened in the campaign — and what to expect when results roll in after polls close at 7:30 p.m.

1. The candidates

Politically radioactive in the wake of the 2018 scandal, Harris declined to run in the new election, and Republicans nominated state Sen. Dan Bishop in May. On the Democratic side, 2018 candidate Dan McCready is back for a second bite of the apple. A Marine veteran who started a solar-power investment firm, the 36-year-old fits the fresh-faced, moderate mold of many of the Democrats’ most successful 2018 candidates. And buoyed by the national attention he received from Democrats who believe he was cheated out of a congressional seat, McCready has also raised more than $4.8 million in total contributions between Jan. 1 and Aug. 21. By contrast, Bishop has raised less than $1.7 million in total contributions.

But conservative PACs have more than closed the gap. Led by the National Republican Congressional Committee, as of Monday, outside groups had spent more than $6.8 million to campaign either for Bishop or against McCready. Taking both campaign and outside spending into account, pro-Bishop forces have spent at least $8.6 million so far this year, and pro-McCready forces have spent $8.4 million.

Last year’s election fraud has played only a small role in this year’s campaign; according to Roll Call, it has surfaced mostly in the smaller, eastern part of the district where the irregularities took place. And instead, McCready has focused on health care — the same issue that helped Democrats flip the House in 2018 — attacking Bishop for voting against a bill to inform patients about low-cost prescription drugs and opposing Medicaid expansion. Meanwhile, Bishop and his allies have hammered McCready for his ties to an organization that lobbied against lower renewable-energy standards, which they claim benefited McCready’s business at the cost of higher utility bills for the general public.

Republicans have also tried hard to nationalize the race. While McCready has distanced himself from the “crazy aspirational things” being discussed by the Democratic 2020 presidential candidates, President Trump has starred in Bishop’s closing ad, recorded a pro-Bishop robocall and held a campaign rally for him in Fayetteville on Monday night. That could be a boon to Bishop, as Trump carried the 9th District by 12 percentage points in 2016.

2. The district

Normally, Republicans would indeed have an edge in the North Carolina 9th District. Until January, it was represented by GOP Rep. Robert Pittenger, and according to FiveThirtyEight’s partisan lean metric, it is 14 points redder than the nation as a whole. But we are in a Democratic-leaning national environment (albeit not quite as favorable as 2018), and McCready has already proved himself a strong candidate. In the 2018 general election, Harris got only 905 more votes than McCready, a margin that would have made it the third-closest House race (by percentage points) of 2018.

So it may be a cliché, but the election may well come down to turnout; not all parts of this diverse district may vote in equal numbers. The 9th District runs over 100 miles along the South Carolina border, from Charlotte in the west to Fayetteville in the east. One crucial area to watch will be the part of Mecklenburg County that overlaps with the 9th District — a wealthy, predominantly white wedge of metro Charlotte that has rapidly transitioned from red to blue in the Trump era. McCready won it by 10 points in the original 2018 election, and based on last year’s voting patterns, anything more than that will put him on pace to win districtwide. Even matching that 2018 performance, however, might be enough, since Mecklenburg may constitute an unusually large share of the 9th District vote this year. That’s because Charlotte is also holding its municipal primaries on Tuesday, which could increase turnout in those parts of the district. Even better for McCready, most of the contested races are on the Democratic side, potentially boosting turnout among his base of registered Democrats.

On the other hand, next-door Union County — home to some farther-flung Charlotte suburbs like Indian Trail and Monroe — is still the district’s richest source of Republican votes. If Bishop wins it by more than Harris’s 20-point margin, it will be a good sign for the GOP. Finally, the six smaller counties east of Union are home to a mix of black, Native American and working-class white voters. McCready won those counties by a combined margin of 7 points, but they’re a bit of a wild card for the do-over election, as it’s hard to predict which of these demographics will turn out for such an oddly-timed contest.

3. The polls

We’ve seen four public polls of the 9th District in the last two months, and they all suggest a close race. A poll from late August, sponsored by Inside Elections and conducted jointly by Harper Polling and Clarity Campaign Labs, had the best news for McCready, giving him a 5-point lead when “leaners” were included. However, a concurrent poll, paid for by readers of the Republican-leaning blog RRH Elections, gave Bishop a 1-point edge.

The North Carolina do-over election should be close Public polls of the North Carolina 9th District conducted in the last two months Results Dates Pollster Sample Bishop (R) McCready (D) Margin Sept. 5-6 Co/efficient 1175 LV 44% 44% EVEN Aug. 26-28 RRH Elections (R) 500 LV 46 45 R+1 Aug. 26-28 Harper Polling/Clarity Campaign Labs 551 LV 44 49 D+5 July 15-18 ALG Research (D) 450 LV 46 46 EVEN Source: Polls

Although McCready has a slight lead if you average the polls, remember that polls of U.S. House elections are not as precise as those for president or Senate — since 1998, they have been off by an average of 6.2 percentage points. And according to CNN, the true margin of error of polls of special U.S. House elections in recent years is ±13 percentage points! Basically, these polls tell us that any outcome is possible in the 9th District except a blowout.

4. The bottom line

The 9th District is the district to watch, but it should be noted that it isn’t the only place in North Carolina holding a congressional election on Tuesday. A much lower-profile special election is also taking place in the coastal 3rd District, whose former congressman, Walter Jones, passed away in February. Given the district’s R+24 partisan lean, GOP state Rep. Greg Murphy is expected to easily defeat his Democratic opponent, former Greenville Mayor Allen Thomas. The only poll we have of the contest gave the Republican a 51-40 lead.

But even though the outcome is in little doubt, you should still pay attention to the final margin, as what happens in both the 3rd and 9th Districts could be telling of the national political environment. Strong Democratic performances in special elections, even in safe Republican districts, were some of the first signs of a strong Democratic year in 2018. That said, turnout could be especially low in the 3rd District as a result of Hurricane Dorian, which made landfall there on Friday, limiting our ability to extrapolate the results. But watch this space on Wednesday for an article putting these two election results in the context of other special elections from the past few years.