After months of insisting that no, no, he wouldn't run - and then a long weekend of well maybe - Christie made it final in a news conference at the New Jersey Statehouse. That means it's basically down to Romney and Perry battling to take on President Barack Obama, three months before the first GOP nomination voting.
Christie was the latest, perhaps last, hope of some establishment Republicans who had already been rejected by Indiana Gov. Mitch Daniels, Mississippi Gov. Haley Barbour, former Florida Gov. Jeb Bush, Wisconsin Rep. Paul Ryan and others who declined to run for president in 2012. He's been governor of New Jersey for less than two years, but he's cut the budget, curtailed public sector unions, and dealt with a Democratic legislature with disarming and combative confidence.
Christie disputed the idea that his name was just the latest on that list.
"They weren't searching. They came right to one target, and it was me," he said Tuesday. "And it has always been me." But he said he was sure, "Now is not my time."
There are still other potential challengers. Former Utah Gov. Jon Huntsman is showing some promise in New Hampshire; former Pennsylvania Sen. Rick Santorum has support from social conservatives in Iowa and former Godfather's Pizza CEO Herman Cain is rising in national polls. Former Alaska Gov. Sarah Palin still hasn't said whether she'll run.
But Christie's announcement leaves Perry and Romney as the two Republicans who have the profile, campaign organization, fundraising prowess and early-state promise for a serious run at the nomination.
Within hours, Christie donors started picking sides. The Romney campaign said Ken Langone, the Home Depot financier who helped lead the push to get Christie to run, had jumped on board. Iowa businessman Gary Kirke, who met with Christie earlier this year to urge him to run, announced he would support Perry.
Both Romney and Perry will be pushing for the support of Christie himself, who now could become something of a 2012 GOP kingmaker. He declined to endorse a presidential candidate on Tuesday, but he promised his backing would mean something if and when he does.
"I'm not a halfway kind of guy," Christie said.
His support could help give Romney credibility among the tea party conservatives who haven't fully embraced the Massachusetts governor. And it could give Perry a way to quiet concerns about his viability.
Whoever wins, Christie 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."
The race's two-man dynamic has already been on display. Romney's campaign didn't bother to attack his Republican opponents, instead focusing on Obama, until Perry joined the race. In the weeks since Perry announced his campaign, the two men have gone after each other on immigration and Social Security. Perry's campaign is focused almost solely on beating Romney.
"We're not running against Herman Cain," David Carney, Perry's top strategist, said in a recent interview.
Christie's declaration is a relief for Romney. The pugnacious, East Coast, blue-state governor has a profile that's similar to the former Massachusetts governor's - and they draw from much the same pool of money and support. GOP establishment figures, donors and luminaries who were encouraging Christie to jump in might now try to help Romney. And the moneyed, business-minded donors in New York and New Jersey who were waiting on Christie are now free to back the technocratic Romney, a former venture capitalist.
For Perry, Christie's exit is more complicated. Now, he'll only have to worry about positioning himself against one candidate. He won't have to worry about losing his conservative, tea party support to the budget-cutting New Jersey governor. Romney has gone largely unscathed in recent debates as news and interest has focused on new entrant after new entrant; now it's more likely that upcoming debates will force Romney to answer tougher questions.
But Romney also won't have to worry about attacking anyone besides Perry - and Obama. And Perry has run into trouble dealing with his own vulnerabilities. He spent the past weekend in New Hampshire defending his record on immigration at town hall meetings. And now he's facing questions about a family-leased hunting camp branded with a racially insensitive name.
Both Perry and Romney will now begin to scramble for the donors who had been waiting on Christie. Romney has already proven he's the Republican race's financial leader, bringing in $18 million during his first quarter as a presidential candidate. Perry hasn't yet had to file a financial report, but aides say his numbers will show he is competitive with Romney.
Still, with Obama and the Democratic Party set to raise close to $1 billion for the general election next year, those numbers don't seem so high.