Most states allow private citizens to challenge someone else’s eligibility to vote, though the rules vary by state. In many instances, such challenges are related to claims that someone has moved from a county or state and so is no longer eligible to vote there. 

Until recently, these challenges had been relatively limited. Now there has been a surge in some pockets of the country, fueled by conspiracy theories about the 2020 election…

https://19thnews.org/2022/09/georgia-elections-voter-challenges/