Six percent of Texas’s voters—over 1.2 million people—have had their voter registrations suspended, and many might not even know about it.

The designation, which means that the voter’s county doesn’t know their address or thinks they’ve moved, doesn’t stop people from voting in November’s midterm elections, but it does make the process more difficult. If a voter shows up on Election Day and their registration is suspended, they have to fill out a “statement of residence” form, and if they’ve moved to a new county, they’ll either be required to vote in their old one or be given a provisional ballot, The Dallas Morning News reported.

The suspended registrations span the whole state, but also some of Texas’s largest counties, including Dallas County, where more than 129,000 voters are suspended; 56,000 voters in both Collin and Denton counties; and over 73,000 voters in Tarrant County.

Voters have until October 5 to update their registrations and can check their status on the Texas secretary of state’s website, at a county election office, or by mail. But with a number as high as 1.2 million people, the message may not reach many voters in time—especially if they haven’t moved and it’s the fault of a clerical error.

That margin could also be pivotal in a state where polls are close in multiple races, especially the Senate, where Democratic state Senator James Talarico has a narrow edge over Republican Attorney General Ken Paxton. Texas is also cooperating with the Trump administration’s attempts to take control of elections by handing over its voter rolls. If a significant number of Texans are blocked from voting on Election Day, that could make all the difference in what the Senate looks like the next four years.