"I think [Reid] is wrong. I did not examine every one of those tax returns. I had a team — we vetted a whole bunch of people, I didn't go through every one," McCain said.

But he denied that concerns about Romney's tax situation were responsible for choosing Alaska Gov. Sarah Palin over Romney as running mate.

"C'mon — is that the same reason I didn't pick Tim Pawlenty and nine or 10 others?" McCain said. "No, the reason I picked Sarah Palin was I thought she was the best candidate at the time."

McCain was joined on the panel by Sen. Kelly AyotteKelly Ann AyottePoll: Potential Sununu-Hassan matchup in N.H. a dead heat  Democrats facing tough reelections back bipartisan infrastructure deal Sununu seen as top recruit in GOP bid to reclaim Senate MORE (R-N.H.) and Sen. Lindsey GrahamLindsey Olin GrahamThe Hill's 12:30 Report - Presented by Facebook - Biden meets with lawmakers amid domestic agenda panic The Hill's Morning Report - Presented by Alibaba - House Democrats plagued by Biden agenda troubles Graham tries to help Trump and McConnell bury the hatchet MORE (R-S.C.), who both also denounced Reid's ploy. The Senate majority leader said earlier this month that an anonymous source familiar with Romney's tax records had told him the candidate had avoided paying taxes for a decade.

Ayotte called the charges "sad and disappointing," while Graham said he thought Reid was "making it up."

The South Carolina lawmaker went on to call Reid's accusations "beneath the Senate, beneath his job as majority leader, and he's making it up, he wants to win too badly, and that's what's wrong with America."