Sen. Marco Rubio, R-Fla., is winning applause for his potential 2016 presidential bid the old fashioned way: quietly raising money, wooing key constituencies and adding his voice to significant issues, but not just for the sake getting headlines.

While some of his competitors like Sens. Rand Paul and Ted Cruz are being more open with their run for the White House, Rubio is playing it cool, and donors and supporters who don't want him to peak too early are happy with his approach.

“I’ve been impressed most with Rubio,” said an executive with a multi-million-dollar GOP Super PAC. “He’s been going about it the right way. The others are peaking too soon,” added the source.

On the surface, the popular senator is working overtime to help the GOP win control of the Senate while also spelling out a conservative agenda for candidates to run on, including education reform and an anti-poverty agenda.

“He's been busy,” said a Rubio supporter. He raised over $1 million in the first quarter for his three election committees and has over $3 million on hand among them. He had fundraisers in Washington state, California and Texas this month.

The conservative also gave a well-received speech at the NRA's annual meeting in Indianapolis and next week will travel to New Hampshire to help local Republicans. And he recently spoke at Google, which supporters said helped him with fans of high-tech and younger voters.

“Right now, I’d say he’s a top pick” for the 2012 GOP primaries, said another major Republican donor.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at