In a dramatic turnabout, Sen. Marco Rubio of Florida has swiftly catapulted to the head of the pack of Republican presidential aspirants. The poll from Quinnipiac University took pundits and pols by surprise -- it’s been barely a week since Rubio formally launching his campaign and stepping up his fundraising efforts.

Rubio, 43, the son of working-class Cuban refugees and a former speaker of the Florida House, kicked off an ambitious campaign for the 2016 GOP presidential nomination April 13 calling for a “new American century” and rejection of the “stale leadership” from older Democrats and Republicans alike. At the same time, he delivered a message for former Florida governor Jeb Bush, his one-time mentor but now likely rival for the 2016 GOP presidential nomination:

“I’ve heard some suggest that I should step aside and wait my turn,” he said. “But I cannot because I believe our very identity as an exceptional nation is at stake and I can make a difference as president.”

Related: Rubio, His Eye on 2016, Vows a ‘New American Century’

Until now, Rubio has been a second-tier contender in the national polls. But in the new Quinnipiac survey, Rubio garners the support of 15 percent of Republican primary voters, followed by Bush with 13 percent and Wisconsin Gov. Scott Walker with 11 percent. No other candidate in the crowded field tops 9 percent, including the two other announced Republican presidential candidates, Sen. Rand Paul of Kentucky and Ted Cruz of Texas. Fourteen percent of those surveyed were undecided.

On the Democratic side, former Secretary of State Hillary Rodham Clinton – who formally entered the race last weekend and then launched a low-key listening tour in Iowa and New Hampshire -- continues to dominate the Democratic field, with 60 percent. She is followed by Vice President Joe Biden with 10 percent and Sen. Bernie Sanders of Vermont, an independent, with 8 percent. Former Maryland Gov. Martin O’Malley, who signaled recently he likely would challenge Clinton, has just 3 percent, while 14 percent are undecided.

Related: Here’s an Economic Agenda for Hillary Clinton

Tim Malloy, assistant director of the Quinnipiac University Poll, said in a statement, “This is the kind of survey that shoots adrenalin into a campaign. Marco Rubio gets strong enough numbers and favorability ratings to look like a legit threat to Hillary Clinton.”

Indeed, in a hypothetical general election matchup, Clinton gets 45 percent of likely voters to 43 percent for Rubio. She leads other top Republicans as follows:

45 – 40 percent over New Jersey Gov. Chris Christie

46 – 42 percent over Rand Paul

47 – 42 percent over former Arkansas Gov. Mike Huckabee;

46 – 39 percent over Jeb Bush;

46 – 41 percent over Scott Walker;

48 – 41 percent over Ted Cruz.





Related: Marco Rubio: 17 Things You Should Know About Him

The national survey was conducted from April 16 to 21. Quinnipiac University pollsters surveyed 1,353 registered voters nationwide with a margin of error of +/- 2.7 percentage points. Live interviewers called land lines and cell phones. The survey includes 567 Republicans with a margin of error of +/- 4.1 percentage points and 569 Democrats with a margin of error of +/- 4.1 percentage points.

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