ABC News’ Michael Falcone ( @michaelpfalcone ) reports:

Despite the begging, pleading, urging and cajoling Chris Christie’s showed on Tuesday that, at least when it comes to his presidential ambitions, he is a politician of his word.

“New Jersey,” Christie said, “whether you like it or not, you’re stuck with me.”

And Christie is stuck with New Jersey.

“I fought hard to get this job, and my job here isn’t done,” Christie said during his nearly 50-minute news conference at the State Capitol in Trenton. “And it just never felt right to me to leave now.”

It also means Republican voters are stuck with their current field of candidates. Mitt Romney has regained his front-runner status, but he still only polls around 25 percent support. And the needle hasn’t moved for him in months. Rick Perry has joined the field of candidates who have begun to flame out for Republicans, with his support flagging.

A wildcard late entrance from Sarah Palin could still throw the Republican field into disarray. But for now, it appears that the competitors are locked.

Christie is unlike Palin, who left her job as governor before her first term ended in Alaska. He acknowledged on Tuesday that he spent some time rethinking his initial refusal to run, before finally deciding just last night to go with his first instinct. He talked of a “commit to New Jersey that I simply will not abandon” and the “unfinished business” he didn’t want to leave behind.

While Christie may have been earnest about his reasons for passing up a 2012 presidential bid, there’s no question the governor has an eye on his future.

“If this guy gets bounced from New Jersey, it doesn’t exactly improve his presidential prospects in 2016,” American Enterprise Institute scholar Norm Ornstein told ABC News.

Even as Christie has spent the last few months politely declining invitations from national Republicans to join the race for the GOP nomination, Christie faced rising and falling approval ratings at home, and as Ornstein pointed out, the prospect of a tough re-election fight in 2013.

And, as much as Christie might want to remain focused on state issues, his status as a national political figure will lead to another inevitable round of speculation about his prospects as a potential running mate for the eventual GOP presidential nominee. Christie had to fend off questions about his interest in the vice presidential slot at his news conference on Tuesday.

“I’m not going to preclude any employment in the future,” Christie said, but added later: “I don’t think there’s anybody in America who would necessarily think that my personality’s best suited to being number two.”

At first glance, Christie does not look like the ideal vice presidential candidate. He’s unlikely to put New Jersey in the Republican column and he won’t necessarily help deliver a specific bloc of voters. Compare Christie to Florida Sen. Marco Rubio, who comes from a crucial battleground state and could also help turn out the Latino vote for the GOP.

If Christie is not asked or turns down a vice presidential offer, he faces the prospect of a Democratic-controlled state legislature that could be “more adversarial legislature than he’s had in the past” according to Brigid Harrison, a professor of Political Science and Law at Montclair State University in New Jersey, who specializes in state politics.

“The Democrats will be more reluctant to cow-tow to his agenda than they have over the past two years,” she predicted. Despite his talk about working across partisan lines, Christie has ruffled more than a few feathers among Democrats and their union allies who have been a target of his since he took office in 2010.

And while Christie’s approval rating in New Jersey is back up above 50 percent, according to recent polls, it dipped significantly over the summer, revealing a potential vulnerability.

“To some degree his credibility is going to ride on whether he can continue to be the guy who takes on the unions and the Democratic power structure while showing” that he can compromise, Ornstein said.

All of that is likely to leave his opponents salivating at the prospect of neutralizing him as a threat — both in New Jersey and nationally. With potential Democratic prospects like Newark, N.J. Mayor Cory Booker and Rep. Frank Pallone, D-N.J., on waiting in the wings as potential gubernatorial rivals, Christie could face an uphill battle to win another term in Trenton.

“He will have the target on his back,” Professor Harrison told ABC News.”National Democrats will be going after him. New Jersey will be viewed as a bellwether election.”

But it’s also clear that Christie now inhabits a space apart from most other governors. He’s emerging as one of the Republican Party’s most valuable surrogates, and all signs indicate that he will continue to be one of President Obama’s chief critics even if he’s not a candidate who is seeking to replace him.

“Overall he’s failed the American people,” Christie said of the president at his news conference on Tuesday — just a week after he issued a similarly scathing critique of the president at the Ronald Reagan Presidential Library.

“There’s no substitute for knowing how to lead,” he said. “Everything else you can be taught — you can’t be taught how to lead and how to make decisions.”

More major speeches like that seem certain to be in Christie’s future.

Though he may have a national platform, Christie’s prospects on the national political stage may also be in need of a reality check.

In a new ABC News-Washington Post poll that included Christie’s name, the New Jersey governor received the support of just 11 percent of Republicans and Republican-leaning independents when he was pitted against the current GOP field.

“I think maybe a better question for Chris Christie is not why he did not get into the race, but why he was thinking about it in the first place,” noted ABC pollster Gary Langer. “It was really not a good fit.”

Now the fight begins among the Mitt Romney and Rick Perry teams to capitalize on Christie’s no-go. That could pay dividends for Romney, who seems more likely to attract Christie supporters. And each campaign is already trying to poach the New Jersey governor’s roster of high-powered donors. The Wall Street Journal reported on Tuesday that Romney has already scored a big one: Ken Langone, the venture capitalist who had been one of the most ardent voices for Christie to jump into the race.

ABC’s Z. Byron Wolf contributed reporting.