Sen. Marco Rubio of Florida on Wednesday won the coveted backing of South Carolina’s governor, Nikki R. Haley, bringing together two of the youngest Republican rising stars at a moment when their party is facing difficult questions about whether instead to look to its past or to political outsiders for leadership.

Coming just three days before the South Carolina presidential primary, Haley’s endorsement could provide Rubio with a crucial lift Saturday. But it may also help him beyond, by associating him with a widely admired leader who, as a woman and a minority figure, shatters traditional perceptions of a Republican politician.

Together, the two 44-year-olds — Rubio, the son of Cuban immigrants; Haley, the daughter of Sikh immigrants from India — hope to form a powerful contrast to an older generation of Republicans who have long controlled the party and are loath to relinquish power.

“I wanted somebody that was going to go and show my parents that the best decision they ever made was coming to America,” Haley, explaining why she had picked Rubio, told more than 500 enthusiastic, sign-waving supporters who stood in the cold outside a warehouse for an evening rally here.

Potential bridge-builder

Haley’s bucking of conservatives in two recent high-profile instances — calling for the removal of the Confederate battle flag from the state capitol in Columbia, and then criticizing Donald Trump’s politics as divisive — elevated her within the Republican Party as a potential bridge-builder to voters who have become disenchanted with a party they see as unwelcoming.

Rubio is counting on Haley’s embrace to draw a bold line under his campaign promises of ushering in a new era of conservatism led by younger, optimistic leaders.

“We have to win. Not just this election — we have to win the future,” he told the evening crowd in Chapin. “We have an incredible opportunity not just to unite the conservative movement but to grow it, to take our message to people that don’t vote for us now, to people that for 25 years have been told the Republican Party only cares about the rich people.”

Jeb Bush: 'I'm disappointed'

As Rubio and Haley banded together in the name of turning the page, Jeb Bush, the former Florida governor, was essentially asking voters here to do the opposite. Bush, 63, has been campaigning this week with his brother, former President George W. Bush, in a nostalgic tour celebrating the Bush legacy.

Speaking to reporters as he campaigned outside Charleston — at a country club, which seemed only to accentuate the generational divide — Bush tried to remain upbeat, but said he was unhappy nonetheless at Haley’s decision.

“I’m disappointed,” Bush said. “She’s a very good governor. And should I win the nomination, there will be a role for her in the campaign, trust me.”

A major boost for Rubio

For Rubio, who is eager to put behind him an embarrassing fifth-place finish in the New Hampshire primary, Haley’s endorsement could provide a much-needed jolt. And it seemed to bolster what Rubio’s aides had been saying privately for the last several days: that the Florida senator was climbing to finish in third place, if not in second place, here Saturday.

The tightening dynamics of the race were also evident Wednesday in the sometimes bitter, sometimes bizarre tones of the other Republican contenders.

A target on Ted Cruz's back

Sen. Ted Cruz of Texas, who is second in most polls here, found himself under furious assault from two sides, with Rubio and Trump, who leads in the South Carolina polls, accusing Cruz of running a dishonest campaign and of deploying sleazy last-minute tricks, like push polls and Facebook posts to deceive voters. Trump has sent a cease-and-desist letter to the Cruz campaign demanding it pull an ad that quoted Trump saying in 1999 that he was “very pro-choice.”

Cruz, rattled and visibly agitated at having his credibility impugned by two rivals he believes have taken their own liberties with his record, held forth in a news conference for 40 minutes Wednesday to assail both men. He called Rubio “Donald Trump with a smile.” His retort to Trump’s lawsuit threat: Sue me.

“I may well not use outside counsel,” said Cruz, a lawyer who has argued cases before the Supreme Court. “I may take the deposition myself.”

Trump threatens lawsuit

In a statement after Cruz’s remarks, Trump called Cruz a liar and threatened legal action over a separate alleged offense: his contention that Cruz’s Canadian birth disqualifies him from being president.

“If I want to bring the lawsuit regarding Sen. Cruz being a natural-born Canadian, I will do so,” Trump said, adding mockingly, “Time will tell, Teddy.”

Rubio seemed content to leave the lawyers out of his feud with Cruz. But he, too, assailed Cruz’s integrity, saying that tactics like a phony post on Facebook — depicting Rep. Trey Gowdy of South Carolina renouncing his endorsement of Rubio — showed Cruz’s lack of character. (Cruz repeatedly denied he had anything to do with the post.)

“It does reflect the kind of campaign you’re running and what you’re capable and willing to do in order to win,” Rubio told reporters at a stop in Mount Pleasant on Wednesday morning. “Ted, unfortunately, has proven that he’s willing to say or do anything to get elected. I don’t think that’s a positive thing to see in a president.”

The tag-teaming by Trump and Rubio could be harmful for Cruz, whose campaign is so reliant on an image of conservative purity and fidelity that he often gives speeches in front of a backdrop reading “TrusTed.”

Bush sought Haley endorsement

Bush, meanwhile, turned most aggressive toward Rubio. And the Haley endorsement seemed only to unleash more of his hostility.

Responding to Rubio’s criticism that Bush lacked foreign policy experience, Bush was dismissive: “It’s hard for me to be lectured to by a gifted young guy who thinks that going to a committee hearing means that you know something about the world.”

Bush had worked hard to convince Haley to endorse him instead. He told NBC News this week that her endorsement would be “the most powerful, meaningful one in the state.” An aide to Bush said she called him personally Wednesday to let him know her decision.

People close to Haley said she always personally liked Rubio and never seriously considered endorsing Cruz. Haley also shares an influential political consultant, Jon Lerner, with the “super PAC” supporting Rubio’s campaign, Conservative Solutions PAC.

Haley's own destiny at stake

Though the state’s senior senator, Lindsey Graham, had personally lobbied Haley to endorse Bush, Haley decided to go with Rubio because she believed he represented Republicans’ best chance to stop Trump and to win in November, her associates said.

Her well-timed move could also bolster Haley’s own fortunes if Rubio were to become the nominee: She has frequently been mentioned as a likely Republican vice presidential candidate.

Nodding to the consternation her endorsement had already stirred, Haley grabbed the microphone from Rubio after he had spoken Wednesday.

"This is one of many bruises I will take for Marco Rubio," she said. "So if I'm going to do that, I need you to go out on Saturday. I need you to make sure we have the highest turnout we've ever had in South Carolina," she continued. "We make presidents. Let's make Marco Rubio the next president!"