Christie, who considered a 2012 presidential bid of his own before endorsing former Massachusetts Gov. Mitt Romney, is already at work on his speech to the convention in Tampa, Fla. 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 assignment. 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."
The Romney campaign said Tuesday that Florida Sen. Marco Rubio will introduce Romney at the convention. Rubio campaigned with Romney in Miami on Monday, and both Rubio and Christie were believed to be under consideration to join the GOP ticket as Romney's running mate - a role that was filled Saturday by Wisconsin Rep. Paul Ryan.
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.
"As governor of New Jersey, Chris Christie has proven how bold Republican leadership gets results," Republican National Committee Chairman Reince Priebus said in a statement. "He has fearlessly tackled his state's most difficult challenges while looking out for hardworking taxpayers."
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 that his influence is waning and has left the door open to a future 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."
Associated Press writer Kasie Hunt in Miami contributed to this report.