(CNN) – Republican Sen. John McCain said Tuesday that Mitt Romney's tax returns in the 2008 vice presidential vetting process did not factor into the senator's decision to pick Sarah Palin instead.
Romney, who had ended his own presidential campaign in the 2008 GOP primary, reportedly provided McCain's team with more than 20 years of tax returns, significantly more than the amount of information Romney has made public this time around.
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Democrats, in their full-court press urging Romney to release more tax returns, now ask why Romney was willing to give so many documents to McCain, but won't do the same publicly this year. Some have questioned whether McCain saw something in Romney's tax information four years ago that discouraged him from picking Romney as his running mate.
"Of course not," McCain told Politico on Tuesday. "I don't know what depths these people won't reach. Obviously, it's just outrageous. That's just outrageous. It shows the – it's so disgraceful for them to allege something that they have absolutely no knowledge of."
McCain maintained his campaign selected Palin, who was a first-term governor of Alaska at the time, "because we thought that Sarah Palin was the better candidate."
He continued: "Why did we not take [Tim] Pawlenty, why did we not take any of the other 10 other people. Why didn't I? Because we had a better candidate, the same way with all the others. ... Come on, why? That's a stupid question."
Romney has released his 2010 tax returns and an estimate for 2011, with a promise to release the official documents for last year once they're ready. He filed an extension with the Internal Revenue Service, meaning he may not put out his returns until the October filing deadline.
McCain has consistently stood by his pick in Palin, saying she was the most qualified person and most capable of energizing the Republican Party.
"I admire and respect her and I'm proud of our campaign," McCain said on Fox News in March, answering questions about a recent HBO film about the McCain-Palin ticket. "I'm grateful she ran with me."
McCain, who endorsed Romney this cycle one day after the Iowa caucuses, took issue with reports of his comments on Tuesday.
"Some in the media have chosen to take my answer today, in response to the question of why I did not select Governor Romney as my vice presidential nominee, out of context. I selected Sarah Palin because she was the best fit for my campaign, and my decision had nothing to do with the bogus tax return attacks currently being waged by the Obama campaign. I have the highest respect for Governor Romney and his record of public service, and he will make an outstanding president," McCain said in a statement.
– CNN's Robert Yoon contributed to this report.