The presidential campaign of Sen. Barack Obama (D-Ill.) on Tuesday denied Republican charges that the campaign is paying ACORN activists to register voters.

The community organizing group has been targeted by the GOP for alleged participation in voter fraud. In a conference call with reporters, Obama campaign officials said they never paid ACORN to register voters, asserting that the campaign’s voter-registration effort is separate from ACORN’s.

The ACORN charges come as Obama’s GOP opponent, Sen. John McCain of Arizona, continues to link Obama to former Weather Underground member William Ayers. That the Obama campaign is responding to the ACORN attacks instead of focusing on its core message — fixing the economy — could be seen as at least a tactical victory for McCain.

The officials on the call, Obama campaign manager David Plouffe and general counsel Bob Bauer, did not deny reports that the campaign paid $800,000 to an ACORN affiliate, Citizens’ Services Inc., but they said the money was for canvassing and not voter registration. They charged that efforts by the McCain campaign to raise the issue were a “smokescreen” for what were in fact voter-suppression efforts by the GOP.

Earlier today, former Sens. John Danforth (R-Mo.) and Warren Rudman (R-N.H.) held a press conference in Washington to offer to cooperate with Democrats in an effort to avert potential Election Day voting problems. Bauer and Plouffe dismissed the overture as insincere.