In Wednesday night's debate, Obama addressed the allegation.
"Apparently what they're doing is they were paying people to go out and register voters. Apparently, some of the people who were out there did not really register people, they just filled out a bunch of names," Sen. Obama said. "It had nothing to do with us."
The registration cards in question have been the focus of investigations around the country, including right here in Philadelphia.
Deputy Election Commissioner Fred Voight says Philadelphia had 350,000 voter applications. Of those, 41,000 were people who were already registered, or had already filled out registration forms.
The remaining 12,000 had other irregularites. Voight says ACORN is responsible for the largest number of registration cards. 1,500 of those are now in the hands of the U.S. Attorney for investigation.
But Voight adds that the numbers are not alarming because of the enormous number of people registering this year. He added that he does not believe this is politically motivated.
"Part of it relates to how they hire their people. They hire people who are desperate for money and they have "x" numbers that they have to turn in, and if they don't they get fired," Voigt said.
ACORN member Junette Marcano says mistakes are inevitable and the organization has a system in place meant to catch invalid or questionable applications before they're handed over the to Board of Elections.
In fact, ACORN itself flagged more than 1200 cards they deemed problematic.
When asked why she thought the group was being targeted, Marcano said "Because we are doing massive voter registration and there is a move to supress the constituents we are registerting because they are low and moderate income."
House Republicans are calling for a Justice Deptartment investigation of ACORN.
Local election officials do not believe all of the problems with registration cards will be resolved by election.