Sen. John McCain (R-Ariz.) said he and Rick Santorum didn't get along as U.S. senators.
"I'm not sure that he's too extreme, but I did not get along with him when I was in the United States Senate," said McCain on NBC's "The Tonight Show With Jay Leno" Wednesday.
The Arizona senator, who is supporting Mitt Romney for president, told Leno that he had "strong differences" with the former Pennsylvania senator. He accused Santorum of supporting earmarks and pork barrel spending, including the so-called "Bridge to Nowhere."
"My favorite was I think we spent about $50,000 one time to study the effect on the ozone layer or flatulents in cows — now, I always wondered about the testing procedures," he said.
"How do you get out of that job?" asked Leno.
"Unemployment would have to be awfully high," joked McCain.
"The point is this earmark and these projects were based only on the influence of the senator rather than the merits of it. It's a gateway drug to corruption," McCain said.
Romney's campaign has argued that Santorum is not a true conservative because of his support for earmarks.
Santorum has said in the past that while he took advantage of earmarks as a legislator, he didn't abuse them.
Santorum said last week that although he now regretted endorsing Romney for president in 2008, he did it because the alternative was McCain.
"I supported Mitt Romney when it was down to Romney and McCain," Santorum said on Fox News. "I knew John McCain, I knew what kind of conservative he would be, so I landed with Romney."
