Rubio: Decision on 2016 race coming by April

2016 run decision by end of March: Sen. Rubio
2016 run decision by end of March: Sen. Rubio   

Sen. Marco Rubio told CNBC on Wednesday his decision on whether to seek the GOP presidential nomination comes down to where he'd be able to make the most difference—among the new Republican majority in the Senate or in the White House.

"Talking in financial terms," since he was appearing on "Squawk Box," Rubio said he'd probably make his decision "before the end of the first quarter," which runs until the end of the March.

Taking a page out of the presidential candidate handbook, the Florida senator laid out his ideas for shaping the nation's future in a new book, "American Dreams: Restoring Economic Opportunity for Everyone," which went on sale Tuesday.

Read MoreRubio: We need to bring $2T US cash overseas back

"I'm confident about what I'd run on if I decide to run. I'm very confident we have a message that's relevant and will resonate. And I'm confident that we can build an organization that can raise the money and execute a plan that makes us successful," he said in an interview recorded after the show Wednesday.

Making a further case for his credentials, Rubio said, "I've been in the Senate for four years, which is not an insignificant period of time given the fact that our current president was only there for two." President Barack Obama served as a Democratic senator from Illinois before was elected president in 2008.

No candidates on either side of the aisle have officially announced for 2016 yet, but it's widely expected that Hillary Clinton will run for the Democratic nomination.

Rubio said Clinton is weak on the economy, an area in which he believes himself to be strong. "On economic policy, she really hasn't distinguished herself with innovative ideas that are relevant to the 21st century."

Clinton, who had served as Obama's secretary of state, would have a lot of explaining to do about her foreign policy, Rubio said. "She's for sure a continuation of Obama foreign policy since she helped architect it."

On the Republican side, Rubio believes many of the names being bandied about would be strong candidates, but without elaborating said each of them has strengths and weaknesses.

Former Florida Gov. Jeb Bush, who has created a political action committee, appears to be a likely candidate, and Mitt Romney had told donors he is thinking about a third White House bid. New Jersey Gov. Chris Christie's name is still out there. Sen. Rand Paul of Kentucky also seems to be gearing up.

But Rep. Paul Ryan, the GOP vice presidential nominee in 2012, told NBC News on Monday he won't be running. The Wisconsin Republican believes he can make a "big difference" in his new role as chairman of the influential House Ways and Means Committee.

Read MorePaul Ryan won't run for president in 2016

Rubio said he's wrestling with the same question: "Where can I best move the ball. ... Is it, now that we're in the majority, in the Senate? Is it running for president?"

Either way, he vowed to pursue his belief that government has a role to play, "but it's not the primary role."

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