It was Donald Trump’s first debate since he boycotted the Republican showdown in Iowa, but the spotlight Saturday was focused on two first-term senators who are perhaps his biggest threats to the GOP nomination.

Florida Sen. Marco Rubio and Texas Sen. Ted Cruz must have felt they had bullseyes on their chests throughout the debate at St. Anselm College in Manchester.

And the three mainstream governors, searching for a breakout moment after tepid showings in Iowa, had feisty performances at the senators’ expense that gave their supporters reason to cheer.

Rubio was hit with attacks from New Jersey Gov. Chris Christie and former Florida Gov. Jeb Bush, both who painted him as too inexperienced to lead the country and compared him to President Barack Obama, also a senator elevated to the White House.

And Cruz was slammed by retired neurosurgeon Ben Carson for his campaign’s role in spreading inaccurate information at the Iowa caucuses claiming he was dropping out of the race. Trump also painted Cruz as a weak-kneed embodiment of Washington politics.

The candidates in the crosshairs responded in very different ways. Rubio pivoted repeatedly to an assault on Obama’s administration lifted directly from his stump speech. Cruz, meanwhile, sidestepped most personal attacks and apologized to the Cruz campaign while shifting the blame on his miscue to the media.

The pressure on Rubio and Cruz was undeniable sign that the rest of the Republican field sees the two senators as the biggest threat ahead of Tuesday’s first-in-the-nation primary in New Hampshire. As well they should.

Cruz handily won Monday’s caucus, catapulting him into a strong position for when the presidential race turns South. And Rubio’s third-place finish bolsters his case that he – and not Bush, Christie or Ohio Gov. John Kasich – should be the mainstream candidate to unite Republicans.

It was also a chance for the candidates to make a final debate pitch to the state’s notoriously independent-minded voters. And Christie, in particular, seized at the chance to make a lasting impression, taking every opportunity to try to turn Rubio into a punching bag.

Trump, eager to reinvigorate his campaign after finishing as the runner-up in Iowa, got a chance early in the debate to snub a rival. When Cruz passed up a chance to explain his assertion that Trump doesn’t have the right “temperament” to be president, Trump pounced.

“If you noticed, he didn’t answer your question,” Trump said of Cruz. “That’s what’s going to happen with our enemies and the people we compete against. We’re going to win with Trump. People back down with Trump. That’s what I like and that’s what the country likes.”

Cruz also was held to account for his campaign’s decision to tell supporters that Carson was dropping out of the race hours before Iowans began to vote. Carson was returning to Florida for a quick break – not to drop out of the race.

“It gives us a very good example of certain types of Washington ethics. Washington ethics,” Carson said, describing his view of the Cruz campaign’s strategy. “Washington ethics basically says, if it’s legal, you do what you need to do in order to win. That’s not my ethics. My ethics is, you do what’s right.”

Cruz apologized to Carson but blamed CNN for distributing the news and failing to “correct” it on a timely basis.

Rubio, meanwhile, was assailed repeatedly by Christie. In one lengthy attack, Christie painted him as an ineffective senator armed with only a “25 second memorized speech that his advisers gave him.”

“You have not been involved in a consequential decision, where you had to be held accountable,” said Christie. “You just simply haven’t.”

Rubio accused Christie of being too reluctant to return to New Jersey during a January snowstorm, saying his constituents “had to shame you into going back.” But he made Christie’s point for him by repeating the same anti-Obama line from his stump speech four times.

“It gets very ugly when he gets off his talking points,” Christie said of Rubio after one bitter exchange.

At another point, he attacked Rubio for retreating from an immigration measure he worked to pass that would have provided a pathway for undocumented immigrants to stay in the U.S.

“The question was, did he fight for his legislation? It’s abundantly clear that he didn’t. It’s abundantly clear that he didn’t fight for his legislation,” Christie said. “That’s not what leadership is. That’s what Congress is.”

Hoping to rebound after a sixth-place finish in Iowa, Bush opened his own line of attack on Rubio by calling his fellow Floridian a “gifted politician.”

“But we’ve tried it the old way with Barack Obama, with soaring eloquence,” said Bush. “And we got someone who wants to divide the country up.”

Bush, long a favorite target of Trump’s taunts, also had a testy back-and-forth with the billonaire that seemed to rile up the crowd. When Trump ordered his adversary to “be quiet” so he could talk, the audience responded with loud boos. Trump then turned to the cameras.

“It’s all of his voters and the special donors,” he said, as more boos echoed through the arena. “We have all the donors in the audience. And the reason they’re not loving me is I don’t want their money.”

Also under mounting pressure to perform well in New Hampshire, Kasich stuck to the upbeat message he’s embraced on the campaign trail and ducked a few chances to attack his rivals head-on.

“I’ve gotta say, after being here, every one of my 100 town hall meetings in New Hampshire were a lot more fun than what I saw here today, were so much more positive,” said Kasich.

While it might not have seemed like it, the seven candidates who crowded the debate stage represented a significantly smaller Republican field. Kentucky Sen. Rand Paul, former Arkansas Gov. Mike Huckabee and ex-Pennsylvania Sen. Rick Santorum all dropped out of the GOP race after poor showings in Iowa.

Also missing from the debate was businesswoman Carly Fiorina, who fell short of polling standards to make the stage.

She posted to her Facebook page that ABC, which televised the debate, and the Republican National Committee caved to "pressure from the same establishment candidates we beat who are afraid to debate me."