Voters eligible to cast ballots are already being swept up in a grassroots effort to purge the nation’s registration rolls ahead of the 2024 presidential election, a CBS News investigation has found.

Fueled by doubts about the 2020 election, an army of conservative activists is poring over state voter lists, looking for registration errors that can be used to file what are known as voter challenges — questioning the registrations of thousands of Americans.

The undertaking, which includes the involvement of a lawyer tied to former President Trump’s alleged efforts to overturn the 2020 election, tends to affect minority or younger voters who may be statistically more likely to vote Democrat, according to local election officials.