Senate Majority Leader Harry Reid (D-Nev.) is standing by his story that a Bain Capital investor called him recently to tell him that Mitt Romney hadn't paid taxes for 10 years.

Reid's comments came Wednesday, a day after he said he was told by someone who invested in Bain, the venture-capital firm founded by Romney, that the reason the former Republican Massachusetts governor had released less than two years of his tax returns was because he hadn't paid any taxes in over 10 years.

"I am not basing this on some figment of my imagination," Reid said in a conference call with Nevada reporters, according to the Las Vegas Review-Journal. "I have had a number of people tell me that."

As he did when he initially told the story, Reid refused to say who the investor was.

"No, that's the best you're going to get from me," Reid said.

Reid said the focus should not be on Romney.

"The burden should be on him. He's the one I've alleged has not paid any taxes," Reid said. "Why didn't he release his tax returns?"

Democrats have been pushing hard for Romney to release more of his tax returns, saying his refusal to do so shows he has something to hide. Romney has said he's released a sufficient amount of his tax records.

The Democrats' push is part of a larger strategy of casting Romney as beholden more to the wealthy than to middle-class households.