Leading Republican strategists say that if he is serious about a presidential race in 2012, New Jersey Gov. Chris Christie is running out of time to build the kind of national campaign and fundraising organization he will need. But, they added, the tough-talking governor immediately would become a top-tier candidate with a real chance of winning the GOP nomination.

While there is no timetable for him to make up his mind, the realities of the political calendar dictate that Christie must do so in short order.

In Iowa and New Hampshire, home to the first-in-the-nation caucuses and primary, Republican strategists say there is no sign that Christie or his political advisers are laying the groundwork for a run. For instance, Christie has not reached out to Iowa Gov. Terry Branstad (R), a call that prospective candidates normally would make, according to a Branstad aide.

“I haven’t seen the due diligence done,” said Rich Killion, who was Tim Pawlenty’s New Hampshire strategist but has been unaligned since Pawlenty dropped out.

Michael Dennehy, another uncommitted New Hampshire-based strategist said: “It’s quiet and a little weird. If he’s really seriously considering it, when does he start putting calls into New Hampshire?”

But there are other signals that Christie is giving serious consideration to a run. One Iowa businessman, who sought unsuccessfully to draft Christie into the race earlier this year, said he was preparing this week to endorse another candidate, but Christie’s political advisers asked him not to.

“Something’s up now,” said the Iowan, who requested anonymity to discuss private matters. “I was ready to jump, but was told to hold off until next Wednesday.”

While Christie repeatedly had asserted that he had no interest in running for president, sources familiar with his thinking said Friday that he was moved to reconsider by the extraordinary number of pleas this week from prominent GOP donors, leaders and activists for him to make a late entry.

Christie and his team may be analyzing where he might fit into the current field and how big an opening there really is. Republican strategists said Christie would pose as big a threat to Texas Gov. Rick Perry and other tea party-aligned conservatives as he would to former Massachusetts governor Mitt Romney, who has won over many in the party establishment.

“Christie’s a different type of Republican,” said Scott Reed, who managed Robert Dole’s 1996 campaign and is uncommitted in the current race. “He has the ability to transcend the traditional ideological battles for a nomination because of the unique way that he came on the scene — as a tough-talking guy in some really tough times.”

Still, like Perry and Romney, Christie would have to explain some positions he has taken that are out of step with conservative orthodoxy. Three years ago, he said the term “illegal immigrant” should not be used, arguing that “being in this country without documentation is not a crime.”

The current candidates — and most Republican voters — are sharply opposed to people being in the country when they are not authorized to be here and often use the phrase “illegal aliens” to describe them.

“If he gets in, he’ll immediately become the target of attacks,” said Pete Wehner, a onetime adviser to former president George W. Bush. “His record, which most Republicans have only a limited knowledge of, will be scrutinized. And he’ll have to get up to speed on national security issues, which are presumably not his strongest area right now.”

Christie also will have to deal with his own words. In several interviews over the past year, he has said he thought he was not yet ready to be president. Christie became governor, his first elected office, in 2010.

“When I walked into the governor’s office last January there have been some difficult days in the job,” Christie told National Review this spring. “There has never been a day where I’ve felt like I’m over my head, I don’t know what to do, I’m lost. I don’t know whether I’d feel the same way if I walked into the Oval Office a year and a half from now.”

But some Republicans said Christie can overcome his lack of experience because he governed during unusual times.

“Against Romney, Christie can say he governed during a more challenging and recent time; against Perry, he can say that his governorship has had more impact, both in terms of its formal power and its change to the state’s political debate,” said Ramesh Ponnuru, a writer and senior editor at the conservative National Review.

If he decides to run, Christie also faces some important, if unglamorous, challenges of building a campaign organization — building a campaign Web site, mapping out a campaign schedule and identifying precinct organizers in places like Iowa and New Hampshire. He will have to compile the necessary signatures and file the requisite paperwork to get on the ballot in all 50 states. Ballot-access deadlines are fast approaching — New Hampshire’s is Oct. 28; Florida’s is Oct. 31.

“It’s not something that you can flip a switch overnight and you’re there,” said Dennehy, who was a senior adviser to John McCain’s 2008 campaign.

All of this, Christie’s inner circle knows. His top political adviser, Mike DuHaime, managed Rudy Giuliani’s 2008 presidential campaign, while his deputy chief of staff for communications, Maria Comella, was the Giuliani campaign’s deputy communications director.

If Christie runs, Reed said, “his rollout will be everything. If he does enough and he barnstorms the country for seven or eight days, he’ll turn this race upside down. If he announces and goes into a cubbyhole to study for debates and raise money, he won’t define himself well.”

Republicans may cut Christie some slack for getting into the race late — but, as Perry learned, only so much slack. If he does not live up to expectations in debates and on the stump, his momentum could be zapped.

“Coming in late, there’s times you have to shoot from the hip,” Killion said. “People will reward that if it’s done well, because they’ll view it as someone being real. It’s a big challenge, but it’s a big opportunity.”

But, Killion added, “time’s a-wasting, and for anyone in his position, there’s a real short leash on pulling that trigger.”

Staff writer Chris Cillizza contributed to this report