If Jennifer Riley Collins, a former a military intelligence officer who served as head of the Mississippi American Civil Liberties Union, wins her race for Mississippi Attorney General today, she will become the first black woman elected to a statewide office in this historically red state.

But the 53-year-old Democrat has more to worry about than just defeating her Republican opponent. Even if Riley Collins wins a majority of votes, an 1890 Jim Crow-era election law may prevent her from taking office.

After Reconstruction ended and African Americans began seeking elected office, framers from the state’s 1890 Constitutional Convention sought to “secure to the State of Mississippi ‘white supremacy,’” according to a journal of the convention’s proceedings. Accordingly, Mississippi adopted a two-pronged process for winning statewide offices: candidates must not only win a majority of votes in the state; they must also win in a majority of its 122 state house districts — only a third of which are majority black, despite the state having the nation’s largest percentage of black voting-age residents. If a candidate fails to meet the second prong of this unique electoral procedure, the state house decides who wins.

This 1890 provision has come into play only once before, according to NPR. When the 1999 Democratic gubernatorial candidate won the popular vote, but narrowly missed 50% of the votes needed to achieve a full majority, the Democrat-led state house selected the Democratic contender anyway.

But this year at least two races could be tested by the provision. Republicans currently control about 60% of the state’s 122 house seats. If Riley Collins wins the majority vote but fails to secure a majority of house districts, legislators could vote to select her Republican opponent State Treasurer Lynn Fitch. The fate of current Mississippi Attorney General Jim Hood, who is vying to be the state’s first Democratic Governor in nearly two decades, hangs in the same balance.

Riley Collins considers this two-prong test to be unlawful. “The crafters of the constitutional provision were clear that the purpose of the provision was to ensure that no African American was ever elected to a statewide position,” she tells TIME. “I am a proponent of one man, one vote, and this provision runs contrary to that.”

The law is being challenged in court. In May, Leslie Burt McLemore, Charles Holmes, Jimmie Robinson, Sr. and Roderick Woullard sued Mississippi’s secretary of state and the state’s speaker of the house alleging the two-tiered structure violates the U.S. Constitution’s 14th and 15th Amendments, as well as the 1965 Voting Rights Act. “Absent court intervention, the challenged provisions will continue to infringe upon the constitutional and statutory rights of African-American voters in Mississippi, dilute African-American votes, and violate the one-person, one-vote principle in the upcoming general election and in every statewide election for years to come,” wrote the plaintiffs, all of whom are African American. Three of the plaintiffs had to pay poll taxes or pass so-called understanding tests to vote at some point in their lives.

To be sure, Riley Collins faces tough odds winning a majority of votes in the first place. Fully 65% of white voters in the state identify as Republican or Republican-leaning, according to Pew Research Center. And although 76% of black Mississippians identify as Democrats or Democrat-leaning, black voters in the state have showed low to moderate voter turnout as a result of a long history of racist electoral barrier, including poll taxes and literacy tests, which were not banned until the 1960s.

Despite these factors, Hood’s gubernatorial race against sitting Lieutenant Governor Tate Reeves appears to be neck and neck. The most recent polling showed Reeves ahead by only 3%, which was within the poll’s margin of error. Earlier polls showed Hood had a slight advantage, while the nonpartisan Cook Political Report rated the race as “lean Republican.”

Mississippi political consultant Brad Chism, who says he has offered Hood’s campaign advice in a limited capacity, says public polling offers a limited picture in such a tumultuous political news cycle. It’s possible, for example, that the ongoing impeachment inquiry into President Donald Trump obfuscates Reeve’s conservative platform. Chism also questions whether there was sufficient organizational support to turn out African American voters in high volumes. “I have really big questions that the polls won’t answer. We won’t know until tomorrow,” he told TIME Monday evening.

On Friday, a federal judge denied the plaintiffs’ motion to block Mississippi from using the two-step process in Tuesday’s elections. The judge did say, however, that he had “grave concern” about the constitutionality of the law’s construction. He also implied the court could act swiftly should the antiquated law prevent a candidate with a majority of votes from taking office. “The Court will not prejudge those issues, but under those circumstances the case would likely proceed to an expedited trial on the merits,” he wrote in his ruling.

Mississippi’s secretary of state, who was named as a defendant in the lawsuit, has claimed the lawsuit was “about partisan politics” rather than race. But the four plaintiffs argue the election law in question requires African Americans’ preferred candidates to work harder than their opponents to win elections. The rule “creates such a significant disadvantage for candidates preferred by African Americans that they must obtain more than 55% of the popular vote to win a majority of House districts,” the May lawsuit says.

“I’ve always had to do more,” Riley Collins says. “It is, unfortunately, the row that we have to hoe — because everyone has not yet embraced that we are equal.”

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Write to Abby Vesoulis at abby.vesoulis@time.com.