Officials in Ohio have removed tens of thousands of voters from registration lists because they have not cast a ballot since 2008, as the November 8 general elections loom in the United States.

All U.S. states periodically cleanse their voter rolls, but only a handful remove voters simply because they don’t vote on a regular basis.

And nowhere could the practice have a greater potential impact in the state-by-state battle for the White House than Ohio, a swing state that has backed the winner in every presidential election since 1960.

Voters of all stripes in Ohio are affected, but the policy appears to be helping Republicans in the state's largest metropolitan areas, according to a Reuters survey of voter lists.

In the state’s three largest counties that include Cleveland, Cincinnati and Columbus, voters have been struck from the rolls in Democratic-leaning neighborhoods at roughly twice the rate as in Republican neighborhoods.

That's because residents of relatively affluent Republican-leaning neighborhoods are more likely to vote in both congressional elections and presidential contests, historical turnouts show. Democrats are less likely to vote in mid-term elections and thus are more at risk of falling off the rolls.

In the three biggest counties, at least 144,000 voters have been removed, the Reuters analysis found. The statewide total is unclear. Each of the state’s 88 counties manages its own voter rolls, which generally are not made public.

Unlike other voting-rights disputes that have sparked protests and lawsuits, the practice doesn't appear to be driven by one specific party. Both Republican and Democratic officials in Ohio have purged inactive voters over the past 20 years.

"It's absolutely unfair," said Donna Porter-Jones, an organizer at Amos Project, an interfaith group that aims to register 30,000 voters from some of Cincinnati’s poorest neighborhoods ahead of November.