Voting Is Power, aimed at black neighborhoods, was financed by the Democratic Senatorial Campaign Committee because U.S. Sen. Mary Landrieu is up for re-election this year, The New York Times reported.
Republican officials complain the drive has produced as many incomplete, duplicate or fraudulent applications as legitimate ones.
The drive is one of many the Democrats are expected to mount this year. Across the country, only 61 percent of eligible blacks and 54 percent of Hispanics are registered, compared to 71 percent of whites, the newspaper said.
Record numbers of people voted in Democratic primaries this year, and turnout is expected to be high in the general election.
"Party politics is driving up registration at unusually high rates," said Michael Slater of Project Vote.