LACONIA, N.H. – His credibility under attack, Republican presidential hopeful Mitt Romney insisted on Friday that he had "no role whatsoever in the management" of a private equity firm after early 1999, and demanded that President Barack Obama apologize for campaign aides who persist in alleging otherwise.

"This is simply beneath the dignity of the presidency of the United States," Romney said in an interview on ABC, one of several he granted to network and cable stations in hopes of extinguishing the controversy.

Under pressure from Democrats and even some Republicans to release tax returns going back several years, Romney indicated he wouldn't do so. "You can never satisfy the opposition research team of the Obama organization," he told CBS.