"I believe that the central obligation of the federal government ... is providing for the national security," he said during a breakfast briefing for reporters hosted by the Christian Science Monitor. "The next President of the United States needs to be someone who has a clear vision of American's role in the world."
"For governors that's going to be a challenge, at least initially," Rubio added, "since they don't deal with foreign policy on a daily basis."
The argument offers an early look at what the Florida senator's primary pitch would be if he does decide to make a play for the White House in 2016.
As a member of the Senate Foreign Relations and Intelligence Committees, Rubio has been an outspoken critic of Obama's foreign policy, and most recently took the lead in opposing the President's move to thaw diplomatic relations with Cuba.
And with the GOP primary field shaping up to include potentially a dozen prominent Republicans, Rubio's foreign policy experience could potentially offer him a needed boost to break away from the pack.
But on Wednesday he refrained from taking any hits at his potential opponents, calling Bush "a very credible candidate" and defending Romney against critics who say he ran a gaffe-prone and lackluster campaign in 2012.
"I don't necessarily think there were flaws in that candidacy," he said.
"I think oftentimes, we forget that in these campaigns, 90 percent of the outcome is determined by the blocking and tackling of politics. And I think the Obama campaign was a superior campaign operation."
He said, however, he's got the support of his family if he wants to run, and he's "down to the last decision...the fundamental one."
"And that is, where is the best place for me to serve the country at this time in my life, at this time in my career?"
This weekend could bring some clarity to that decision, when his top aides and donors huddle
in Miami Beach to discuss the senator's future.
Rubio's made one thing abundantly clear, however, and he repeated it Wednesday: He won't try to run for both reelection to the Senate and for president at the same time.
"If I decide that I want to be president of the United States, that's what I'm going to run for," Rubio said. "If I decide to make that decision, it will not be with the intention of looking for a Plan B if it doesn't work out."