Republicans on Monday stepped up attempts to undermine Senate Majority Leader Harry Reid's unsubstantiated allegations that Mitt Romney went 10 years without paying taxes, saying Reid and other Democrats' accusations are being orchestrated by President Barack Obama's campaign - specifically his senior campaign adviser David Axelrod.

To that end, Republican National Committee spokesman Sean Spicer noted that Axelrod visited Senate Democrats for their weekly lunch last Tuesday. Later that afternoon the Huffington Post story published with Reid's allegations about the presumptive GOP nominee not paying any taxes.

"You've got to wonder if the so-called source is Axelrod himself," Spicer told CNN. "Hours after meeting with Axelrod, Reid comes out and makes baseless accusations?"

Axelrod flatly denied that allegation, calling it "completely false" and saying he "never had any such discussion."

"Instead of pointing fingers in every direction, they can put the whole matter to rest by simply observing the standard George Romney and a generation of candidates have set by releasing the returns," Axelrod told CNN.

In a separate article posted Monday, the Huffington Post wrote that they interviewed Reid days before Axelrod's visit, making any influence from the top Obama official's Capitol Hill visit impossible.

Reid himself remarked on the dust-up Monday in Nevada, telling reporters the dust-up could be solved by Romney simply releasing his tax information.

"This whole issue is not about me," Reid said. "Mitt Romney's the first presidential candidate since his dad ran not to release his income tax returns. He's released one income tax return and that points toward the Bahamas, Switzerland, and a few other foreign countries. This whole controversy will end very quickly if he releases his income tax returns, like everybody else has done."

Romney has released his tax return from 2010, and an estimate from 2011. He has vowed to release his full 2011 return once it's completed.

Multiple Democratic sources insist Reid made the allegations against Romney on his own, but also admit the Obama campaign is not telling Reid to back off.

Meanwhile, Reid's chief of staff David Krone insisted Monday, again, that he knows who Reid's source is - and that the source is credible.

"I know who this person is, and if I thought this person was not credible, I would say something to Senator Reid. I would try to shut it down. This person is credible," Krone said.

"This person has asked Reid to protect the confidentiality of this person, but it's real," he continued. "This person told him this. This person said it to Senator Reid."

Romney himself pushed back against Reid's accusations twice last week, telling the majority leader to either "put up or shut up" and calling the reports false. Republicans, including RNC Chairmen Reince Priebus, backed up the presumptive GOP nominee Sunday morning on news shows.

"I'm not going to respond to a dirty liar who hasn't filed a single page of tax returns himself (and) complains about people with money but lives in the Ritz-Carlton here down the street," Priebus said on ABC News. "And the fact that we're going to spend any time talking about it is ridiculous."

Sen. Lindsey Graham of South Carolina also came out against Reid's statements, saying the majority leader was "making things up."

"What he did on the floor of the Senate is so out of bounds. I think he's lying about his statement, of knowing something about Romney," Graham said Sunday on CNN's "State of the Union."