COLUMBUS, Ohio — An advocacy group that registered more than a million voters two years ago is wrestling with new allegations of voter fraud and sloppy work just weeks before crucial midterm elections. In Philadelphia, the city’s voter registration office has rejected about 3,000 cards submitted by the Association of Community Organizations for Reform Now since April because of missing information or invalid addresses.

Election officials in three of Ohio’s largest counties have cited problems with hundreds of voter registration cards. Acorn is accused of submitting cards with nonexistent addresses, forged signatures, and, in one case, for someone who died seven years ago.

“In my opinion, there’s a lot of words but little action in terms of fixing the problem,” the elections board director in Franklin County in Ohio, Matt Damschroder, said. County election officials in Denver forwarded about 200 cards to the secretary of state’s office after discovering identical handwriting on signatures.

Acorn, which has about 220,000 members nationally, registered 1.2 million people to vote in 2004 and is running voter registration drives in 17 states this year. The nonprofit dispatches workers and volunteers to poor neighborhoods, gas stations, courthouses, and other places to sign up new voters.