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Mitt Romney chose Paul Ryan for his running mate, but he's making sure to find major convention roles for the other short-listers.

New Jersey Gov. Chris Christie and Florida Sen. Marco Rubio, two of Romney's rumored top choices for the job, will have prominent speaking roles at this year's Republican National Convention. Christie has been awarded the coveted keynote address, while Rubio will introduce Romney on the closing night, sources told Fox News.

Republicans formally announced Tuesday morning that Christie, who considered a 2012 presidential bid of his own before endorsing Romney, would speak in the prime slot in Tampa later this month. Rubio has been tapped to introduce Romney on Thursday night of the convention. GOP officials tell Fox News Rubio is already on a third draft his remarks.

The Associated Press reports Christie has also begun working on his speech for Tuesday night of the convention. His record of cutting his state's budget, curtailing public sector unions and dealing with a Democratic legislature with disarming and combative confidence all were expected to be on display as he looked to fire up his party's base.

"I'll try to tell some very direct and hard truths to people in the country about the trouble that we're in and the fact that fixing those problems is not going to be easy for any of them," Christie told USA Today in an interview announcing his speech. He said he will describe his experiences in New Jersey as evidence that "the American people are ready to confront those problems head-on and endure some sacrifice."

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The keynote speech is the highest profile spot for someone not accepting the party's presidential or vice presidential nominations. The slot has launched many political figures, most notably a little-known state senator from Illinois named Barack Obama in 2004. Four years later, he won the White House.

Christie, already a favorite among fiscal conservatives for his tough talk and take-no-prisoners persona, will find a national introduction of sorts in Tampa and, perhaps, offer the opening steps toward a presidential run in 2016 if Romney loses, or in 2020. The 49-year-old former prosecutor has shown little sign of his influence waning, and he has left the door open for a White House run of his own.

Responding to a question about a 2016 presidential bid, Christie told NBC's "Meet the Press" that he was "going to need a job" after 2013. He added, "So maybe it will be that. Who knows?"

Christie became the first Republican elected New Jersey governor in a dozen years when he defeated Democratic millionaire and ex-Wall Street executive Jon Corzine in 2009. Christie was among the most sought-after guest stars on the GOP speaking circuit and spent much of the recent years traipsing from Connecticut to Michigan and Illinois, appearing in Oregon and Minnesota to endorse fellow Republicans and elevating his own national profile.

Many in the party hoped he would mount a last-minute effort to get on the 2012 ballots. He weighed it and in October 2011 earned headlines when he declared with finality that "now is not my time" to run for president, dashing the hopes of Republicans still searching for someone other than then-front-runners Romney and Texas Gov. Rick Perry.

Christie had insisted for months that he wouldn't run. But then came an intense weekend of reconsideration before he made a firm announcement at a news conference at the New Jersey Statehouse. His decision effectively made the campaign between Romney and the rotating cast of anti-Romneys who rose and fell as each primary came and went.

In leaving the 2012 melee, he said he wasn't seeking the job of vice president.

"I just don't think I have the personality to be asked," he said. "I'm not looking for that job."

But, apparently, he wasn't opposed to going to Tampa to deliver a speech that may rekindle buzz about his own presidential ambitions.

"It's what I accomplish or don't accomplish as governor that will be the springboard or not for me," he told USA Today. "It's not what you say but what you accomplish."

Fox News' Carl Cameron and The Associated Press contributed to this report.