It was about this time five years ago when political strategist David Axelrod sat down and wrote a memo to then-Sen. Barack Obama, who was seriously considering whether to run for president after months and months of saying he would not.

“History is replete with potential candidates for presidency who waited too long rather than examples of people who ran too soon. . . . You will never be hotter than you are right now. . . . In short, there are many reasons to believe that if you are ever to run for presidency this is the time.”

Those words could easily be included in a memo that one of Chris Christie’s advisers might be sending to the New Jersey governor now, for many of the same elements that led Axelrod to encourage Obama to run in 2008 apply to Christie at this moment.

Christie’s blunt style has captured the imaginations of many Republicans, as Obama’s hope-and-change message stirred Democrats then. He is a fresh face in a party that is in transition and looking for something more than it sees on the horizon. He is being encouraged to run by ordinary citizens, wealthy fundraisers and party leaders who see an opportunity for victory in 2012 and don’t want to let it slip away.

Axelrod’s memo contained another piece of advice relevant to Christie’s decision-making, which is that the incumbent president defines the coming election and that, if there is unrest in the country, voters will be looking not for a replica but for a replacement. Whatever negative qualities they see in the incumbent, they will be looking for the opposite.

Axelrod was speaking of the qualities of leadership of then-President George W. Bush that had left the country deeply unhappy. He described them as stubbornness, hyperpartisanship and a tendency to place ideology over reason. Axelrod argued that Obama, better than any other potential Democratic candidate in 2008, fit the moment. “You are uniquely suited for these times,” he wrote.

Five years later, after persistent economic problems and a breakdown in government in Washington, the perceptions of Obama have changed, which is why he is vulnerable in next year’s election. To some Republicans, no one offers a more distinctive alternative to Obama’s style of leadership than Christie.

Republican challengers to Obama will make the argument that both different policies and a different kind of leadership are needed to get the country moving, which was part of Christie’s goal when he spoke at the Ronald Reagan Presidential Library on Tuesday night. He outlined that case against the president in ways designed to draw obvious comparisons with his own hard-charging style.

Christie belittled Obama as a “bystander in the Oval Office” and a chief executive who lacks the courage to lead. “We hope,” he added, “that he will shake off the paralysis that has made it impossible for him to take on the really big things that are obvious to all Americans and to a watching and anxious world community.”

He sought to portray Obama as a passive actor and himself as Mr. Take Charge. There is a simple rule for effective governance, he said: “When there is a problem, you fix it. That is the job you have been sent to do, and you cannot wait for someone else to do it for you.”

If Americans decide they want a replacement for Obama, Christie’s advocates will ask: who better than someone who is bold and brash, someone willing to shake up the system, to get in the face of opponents or of slow-moving legislators or even the voters? Someone, in other words, determined to get results.

It is easy to imagine someone around Christie telling him today: You are uniquely suited for these times. That is the essential case for running, that candidates don’t always get the chance to pick their moment. Bush said in the fall of 1998, as the pressure kept mounting for him to run for president, that he felt “like a cork in a raging river” bobbing his way toward the inevitable decision to become a candidate.

The year 2000 was Bush’s moment, whether or not he thought it would be the ideal time. The same was true for Obama in 2008, whether or not he believed another few years of national experience would have been helpful.

Christie might not get another moment like this. By 2016, if the GOP doesn’t hold the White House, a new generation of Republicans will be ready to step forward to battle for the party’s nomination. Christie might not seem unique or as fresh or appealing by then as he does today.

He might, however, be more qualified to serve as president starting in 2017 than he is today. By that time, assuming he wins reelection in 2013, he will have been a chief executive for seven years. He will have a more complete record in New Jersey for voters to weigh. He will have learned lessons he hasn’t yet. He will, if he applies himself, know the country and the world better than he does now.

Christie exudes self-confidence, but until this latest round of Christie Fever, he has shown some humility in at least one area, which is the question of whether he is ready to be president. He has expressed misgivings about whether he could really do the job as he thinks it should be done.

If he is genuinely reconsidering whether to run in 2012, the most important question he will have to answer is not whether he can win the election, though even that is a difficult question. He might look like the ideal candidate to those urging him to run, but no one comes to the starting gate of a presidential campaign without flaws and liabilities. No one can say with any certainty what kind of national candidate he would be.

Still, the most important question is the one about readiness. Does he believe that, if he were to win, he could effectively lead a country in the throes of serious economic problems and a partisan environment in Washington and nationally that has made governing more and more difficult? That is a deeply personal question, and only Christie can answer it.