Mississippi's U.S. Senate race has come down to a margin of roughly 2,400 votes, and the final result now hinges on the hand-counting of tens of thousands of provisional ballots — a drawn-out process set in motion after a state contractor's flawed address data left thousands of eligible voters marked as inactive.

According to Democracy Docket, Mississippi made thousands of valid voters inactive ahead of the election, in which Democratic challenger Scott Collum currently leads Republican Sen. Cindy Hyde-Smith by about 2,400 votes. Because Mississippi has no recount law, the outcome depends on the counting of thousands of provisional “affidavit” ballots filed in local county offices by voters who showed up at their precincts only to find they were not listed as authorized voters — a delay that has postponed the result.

The disruption traces back to a contract between the office of the state's Republican secretary of state and Experian, a global credit reporting agency. The agreement was intended to keep voter registration lists up to date, on the rationale that people frequently move without updating their registrations. But Experian's data — described by Mississippi Today as riddled with errors — threw thousands of voters into “inactive” status in the months leading up to the general election. Nothing about the arrangement is illegal, though the decision to pay an outside firm to “clean up” the voter registrations without actual verification, notification or updating has drawn pointed questions. Experian is one of the three nationwide credit bureaus — alongside Equifax and TransUnion — whose consumer files are built chiefly from lenders' account data and are used primarily for credit decisions and identity verification, not election administration.

Most affected voters received no notice that their status had changed. They arrived at their local voting precincts only to learn they were no longer listed as registered voters. Rather than a normal ballot, they were handed an “affidavit” document recording their choices, along with a declaration of identification. Provisional voting on this basis is a federal requirement: under the Help America Vote Act of 2002, voters whose eligibility cannot be confirmed at the polls must be offered a provisional ballot, which is counted only after officials verify their eligibility.

Evidence of errors in the credit bureau's work surfaced in its own mailings: Experian sent communications intended to help voters update or fix their registrations to wrong addresses. Under the system, it largely fell to individual voters to check on their own registration status.

The scale of the removals was far from inconsequential. In DeSoto County, 15,000 voters were removed as active voters between the primary and general elections, according to Mississippi Today. Jackson County lost 14,063 and Harrison County 28,291. For many voters, arriving at the polls to find themselves missing from the rolls came as a shock. In all, upwards of 230,000 provisional ballots were cast statewide, with 10,000 to 15,000 still outstanding.

Republican Secretary of State Michael Watson defended the inactivations as a “cornerstone of election integrity,” writing in a social media post: “We're getting multiple calls about people not showing up as active voters, so we wanted to share a few details.”

Watson said the state sends the credit data to counties, which are supposed to verify it before updating their lists. “Thankfully, affidavit voting is used to catch any errors or those who live in the same county but forgot to update their info,” he said. He added that the “extra few minutes” it takes a voter to cast a provisional ballot are “well worth the election integrity added by having cleaner voter rolls.”

Under the process now underway, election canvassing boards in each of Mississippi's 82 counties will review all affidavit votes, checking them against existing voter files for those deemed “inactive” as well as the voters' preferences in the Senate race. Many of the affidavit voters had been on the same registration rolls for 20 or 30 years. The counting is being conducted by hand, under the watchful eye of lawyers for both major parties and, likely, federal monitors — with the size of the Democratic majority in the U.S. Senate potentially at stake.

Critics ask a pointed question about the verification stage: if officials are relying on the already-faulty Experian data to cross-check voter files, aren't more errors almost certain? The dispute sits within a tension familiar to election officials nationwide: registration lists must be maintained as voters move, die or re-register elsewhere, yet removals made on imperfect data risk catching eligible voters, who then bear the burden of correcting the record themselves.

“Credit bureau data was never intended to be used to maintain voter rolls, and using the wrong data for the wrong purpose can lead to serious harm,” said Sydney Saubestre of the Center for Democracy & Technology. “In this case, Mississippi undermined access to voting, a fundamental right, by inexplicably using the data broker Experian's data to ostensibly maintain voter rolls.”

In addition, election officials must verify that each provisional ballot was properly signed by the precinct poll manager and that the voter provided identification within five business days.

Observers note that none of these complications would have emerged had the contest been a blowout rather than a virtual tie. In the days ahead, attention will center on how quickly the 82 county boards complete their hand counts, whether affidavit voters meet the five-business-day identification deadline, and how the boards rule on ballots that turn on those checks — each a factor in a race separated by roughly 2,400 votes.

Terry H. Schwadron retired as a senior editor at The New York Times, served as Deputy Managing Editor at The Los Angeles Times and held leadership roles at The Providence (RI) Journal-Bulletin. He was part of a Pulitzer Gold Medal team in Los Angeles, and his team was part of several Pulitzers in New York.