Election officials across the country have been inundated with dubious complaints about inaccurate voter rolls, which have wasted government resources and sapped taxpayer money spent reviewing lists of registered voters that officials say are already carefully maintained, a CNN investigation has found.

One of the main drivers of the fruitless challenges is a conservative Texas-based nonprofit group called True the Vote, an election-monitoring organization that has long peddled debunked voter-fraud theories. The group’s founder, Catherine Engelbrecht, has called on followers to help clean voter rolls by using an app called IV3 that enables users to research voter data and submit voter-eligibility challenges to local election offices.