A new report from the Washington Post has found that a mistake by election officials who assigned 26 voters to the wrong district might have cost Virginia Democrats a crucial race so close they ultimately lost in a lot drawing, leaving Republicans a majority in the state House of Delegates.

In the 2017 state delegate election for Newport News, Democrat Shelly Simonds initially defeated Republican David E. Yancey by a single vote in a recount. Earlier in the year, Republicans had, in part due to the effective gerrymandering of district lines, secured 51 seats in the House. A Simonds victory would have left the House with a 50–50 split.

But on Jan. 4 this year, after a Republican official contested that one-vote victory by arguing for an ambiguous ballot, the Virginia Board of Elections drew lots to break the tie and pulled Yancey’s name. Democrats lost their opportunity to share power with Republicans in the House.

Now, a review of the election from the Washington Post has found that an apparently innocent mistake by local election officials might have been the true determining factor in that race, as more than two dozen voters, the majority of whom were considered likely Democrat voters, cast their votes in the wrong district.

These voters, according to the Post, lived in a majority-black precinct, and the election officials placed them in a neighboring district because of a mix-up with ZIP codes. In response to the Post’s findings, Democrats blamed Republicans for gerrymandering, and Republicans blamed Democrats in charge of the state Department of Elections and local electoral boards.

According to an earlier analysis by the Post, about 6,000 Virginia voters were placed in the wrong district in 2017, including many who should have been allowed to cast votes in races determined by fewer than 500 votes. In one instance, in last year’s race for the 28th House District near Fredericksburg, 147 people voted in the wrong district, missing out on a race that was ultimately decided by 73 votes. According to the Post, officials are conducting a review of local elections throughout the state.