On this Sunday's Meet the Press, Senator Marco Rubio (R-FL) sidestepped a question about Grover Norquist's tax pledge. Norquist's pledge, supported by many Republican politicians, is a vow to oppose any tax increase and block the closure of tax loopholes.

To a question about whether he would use revenue from closing tax loopholes to pay down the federal deficit, Rubio only said, "I would use revenue from growth."

When pressed further by Meet the Press host David Gregory, Rubio—who is reportedly a potential running mate for Mitt Romney—repeated: "I would use revenue from growth. Which I think, when you talk about loopholes—"

"That wasn't my question," Gregory cut in. "Any closing loopholes— You know what I'm getting at, which is this idea of the tax pledge. Do you consider this— Raising taxes, if you close a loophole, you get new revenue to the government, you use part of it to pay down debt, maybe the majority of it to bring down tax rates."

"I know," Rubio replied, acknowledging that this was a question about Norquist's tax pledge, "but I reject the premise of that. I think that's a false choice."

"Other Republicans in the Senate don't think that's a false choice," Gregory said.

"Well, I think it's a false choice, and here's why. Because I think the issue here is growth."

Norquist's tax pledge has long been Republican dogma, though there have been signs lately that his influence within the party is on the decline. Rubio appeared to be trying to pivot from Norquistian doctrine without alienating conservative anti-tax doctrinaires.

That wasn't the only question Rubio refused to ask. Moments later, Gregory asked him whether he stood by his earlier declaration that he would "under no circumstances" serve as the Republican vice presidential nominee.

Gregory played a clip of a prior appearance Rubio had made on the show, circa May 1, 2011. During that show, Gregory had asked Rubio whether or not he would be interested in being the Republican vice presidential candidate in 2012.

"I don't want to be the vice president of the United States," Rubio told Gregory during that appearance. "I want to be a senator. I want to be a senator from Florida."

Gregory pressed further. "So under no circumstances would you serve on the ticket in 2012."

"No, I'm not going to be on the ticket in 2012."

"Under no circumstances."

"Under no circumstances," Rubio echoed.

Once the clip was over, Rubio joked: "I thought you told me you had burned the tapes." When asked whether he stood by his earlier remarks, he refused to answer.

"I'm not discussing the vice presidential process anymore," he said.