Marco Rubio's team believes nomination could be decided at Republican convention

The best hope of the Republican establishment just a week ago, Marco Rubio suddenly faces a path to his party's presidential nomination that could require a brokered national convention.

That's according to Rubio's campaign manager, Terry Sullivan, who told The Associated Press that this week's disappointing performance in New Hampshire will extend the Republican nomination fight for another three months, if not longer. It's a worst-case scenario for Rubio and many Republican officials alike who hoped to avoid a prolonged and painful nomination fight in 2016.

"We very easily could be looking at May or the convention," Sullivan said aboard Rubio's charter jet from New Hampshire to South Carolina on Wednesday. "I would be surprised if it's not May or the convention."

The public embrace of a possible brokered convention marks a sharp shift in rhetoric from Rubio's top adviser that could be designed to raise alarm bells among Republican officials. Yet days after a disappointing fifth-place finish in New Hampshire and looking up at Donald Trump in next-up South Carolina, Rubio's presidential ambitions are truly facing growing odds.

While he downplayed his dilemma on his first day in South Carolina after the New Hampshire setback, the first-term Florida senator discussed his political challenges at length during an unusual 45-minute question-and-answer session with reporters aboard his campaign plane on Wednesday. He answered questions until there weren't any more, noting afterward that he hadn't held a session that long with reporters since his days as Florida's House speaker.

Promises to be more aggressive

In remarks that were at times personal and others defiant, he also may have simply needed to talk it out to help process his predicament. It also seemed he needed to prove to the political world, himself and his family that he could face the biggest test of his young presidential bid.

"My kids were watching me last night," Rubio said of his nationally televised admission that a poor debate performance pushed voters away. "My kids knew that it didn't go the way I wanted it to go."

"I taught them more last night from that experience, I feel, than any words I'll share. They were learning from that experience," he said.

As he shifts his attention to South Carolina's Feb. 20 contest, the 44-year-old freshman senator wants voters to know he's learned an important lesson from his experience in New Hampshire. Instead of trying to avoid attacking his GOP rivals on the debate stage, Rubio said he's now prepared to fight back when necessary particularly with his party's front-runner Donald Trump.

"I don't need to start these fights, but if someone starts one in the future we're going to have to point out the differences in our records in a sharper way," Rubio said. "I don't think we have the luxury any longer to basically say `Look, I don't want to argue with Republicans.' "

New Hampshire destroyed any momentum Rubio had coming out of Iowa and for now, at least, locks the senator into a messy muddle in his party's establishment wing. Both Ohio Gov. John Kasich and former Florida Gov. Jeb Bush beat Rubio in New Hampshire in the contest to emerge as the mainstream alternative to Trump and Texas Sen. Ted Cruz.

And as senior aides embraced the possibility of a brokered national convention, Rep. Trey Gowdy, R-S.C., said the Rubio operation is "built for a long campaign."

"I don't know of anyone who expected folks to fold up after New Hampshire and go on. There are a lot of candidates," Gowdy said as he was traveling with Rubio on Wednesday. "He's never indicated to me anything other than we're built for the long haul and it's going to be a long haul. But, you're running to be the leader of the free world it's supposed to be a challenge."

Last contested convention 40 years ago

There hasn't been a contested national convention since 1976, yet Republican National Committee officials have already had preliminary discussions about the possibility of no candidate securing a majority of delegates in the state-by-state primary contests.

It's by no means assured that Rubio's candidacy will survive that long.

Despite his popularity among many Republican leaders, he will ultimately need to start winning primary contests to remain competitive especially as Trump and Cruz perform well.

Rubio's team has long expressed confidence about his chances in South Carolina. Yet Rubio downplayed expectations when talking to reporters. "We obviously need to do better than we did in New Hampshire," he said of the state where he finished in fifth place.

Sensing weakness, Democrats and Republicans alike have begun to question Rubio's long-term viability.

"The debate performance hurt. We'll see if he can turn it around," said 68-year-old Rubio supporter Rusty DePass after a Wednesday rally in Columbia. "I'm mad as hell at the people who run his campaign for not having him prepared."

"It was awful," DePass said.