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Amid repeated denials that he has White House aspirations, Sen. Marco Rubio, R-Fla., outlined the criteria for how he is evaluating the GOP presidential field today.

At a Politico Playbook breakfast in Washington, D.C. Tuesday, Rubio said the Republican nominee should demonstrate their ability to use “sound judgment” to make decisions, especially in foreign policy where presidents often have to choose between two “less than ideal” options.

“Let me just say a thing about the presidency, and not about me, but just in general,” Rubio said. “Ultimately what you want in a president is the ability to analyze situations and make decisions based on sound judgment.”

The freshman senator is widely regarded as a prime candidate for vice president, despite his insistence that he will not be on the ticket. Rubio’s popularity in Florida, a swing state that could be vital to securing the Republican nomination, and his ties to the Latino community, a voting bloc that will be similarly vital for the  nominee to beat President Obama, have put him on the short list of possible VP candidates.

Rubio has taken hawkish positions on American military engagement abroad and was one of the first Congressmen to speak out in favor of implementing a no-fly zone in Libya.

“I mean, I’m not running for president okay, but I think for the most part as a senator most of the decision-making processes are similar,” he said Tuesday. “You have to take positions on issues that you are going to be judged by history on them whether you made the right choice or the wrong choice.”

Rubio added: “It’s something I hope I am developing in the United States Senate and it’s the kind of quality I’m looking for from our nominee and from our next president.”

In stark contrast to one of the GOP presidential candidates , Rubio laid out a detailed justification for why he supported U.S. military involvement in Libya, and why such involvement in Syria was probably not a good idea.

“They are two different situations and I’ll outline why,” he said. “Libya had an organized rebellion. They were armed. They were making progress. They specifically asked for a no-fly zone. That’s what they asked for to help them finish the job themselves.

“You don’t have that in Syria,” Rubio continued. “Quite frankly I don’t know if we want that in Syria. I don’t know if there is a military engagement the U.S. could get involved in, even in an international coalition, that could prevent that [mass killings] in Syria the way it was able to prevent it in Libya.”

GOP presidential hopeful Herman Cain struggled through a similar foreign policy question Monday when the Milwaukee Journal-Sentinel editorial board asked if he agreed with President Obama on Libya.

“I do not agree with the way he handled it for the following reason,” Cain said. He then paused before adding, “No, that’s a different one.” After a few seconds of silence the former front-runner tries again: “I gotta go back to — got all this stuff twirling around in my head.”

After a shaky performance at the past two debates, which focused almost entirely on foreign policy, and amid continuing sexual harassment allegations, Cain has taken a tumble in the polls. Compared with last month, when he was statistically tied with Mitt Romney for the top spot, Cain has plummeted 11 percent according to a CNN/ ORC poll released yesterday.

Rubio’s public support, on the other hand, has weathered a recent hiccup over when his parents immigrated from Cuba to America. According to a Quinnipiac Poll out last week, Rubio’s job approval rating in Florida remained unchanged by the controversy, with 49 percent of respondents saying they approve of the job he is doing, the same amount that supported him in September.