From fiery criticism of ObamaCare and the Iran nuclear deal to support for Israel and the rights of the unborn, the top 10 Republican presidential candidates did all they could to define and separate themselves Thursday night during the Fox News debate in Cleveland, Ohio.

The governors on stage, notably John Kasich of Ohio and Scott Walker of Wisconsin, touted their economic records. Texas Sen. Ted Cruz vowed to scrap the Iran deal. Retired neurosurgeon Ben Carson reminded voters in his closing remarks of the professional background that separates him from the rest: “I’m the only one to separate Siamese twins.”

Throughout the debate, Donald Trump was the unrivaled lightning rod, but the prime-time showdown made clear he’s not the only fighter on the stage – or in the race.

New Jersey Gov. Chris Christie reclaimed his reputation as a tough-talking executive, blasting his rivals for their positions on domestic surveillance and entitlements. Kentucky Sen. Rand Paul traded barbs with several candidates, including Christie.

Meanwhile, one-time front-runner former Florida Gov. Jeb Bush found himself on defense several times and largely avoided tangling with Trump on the Fox News/Facebook stage.  

Perhaps the most fiery moment came in an exchange between Christie and Paul. Long-simmering tension between the two exploded when Christie stood by his criticism of the senator for opposing NSA bulk collection of Americans’ phone data.

Paul said he’s “proud of standing for the Bill of Rights,” but Christie called his stance “completely ridiculous” – suggesting he wants to cherry-pick only some data.   

“When you’re sitting in the subcommittee just blowing hot air about this, you can say things like that,” Christie said.

Paul fired back: “I know you gave [President Obama] a big hug, and if you want to give him a big hug again, go ahead.” Christie said the hugs he gave were to the families of 9/11 victims, and then accused Paul of playing “politics,” by using videos of floor speeches to raise money.

The exchange was striking, even in a debate that was tense from the start. Though several rivals stood out, Trump did not hold his fire, either – making clear he’s not softening his approach to campaigning as he picks up steam in the polls.

If anything, the debate signaled the primary race is about to get tougher and is still wide open as 17 candidates vie for the lead with months to go until the opening contests.

Trump, the billionaire businessman front-runner, sparred at the outset of the debate with Paul after refusing to pledge to support the eventual GOP nominee if it’s not him and to swear off an independent run.

“I will not make the pledge at this time,” Trump said.  

Paul accused him of “hedging his bet on the Clintons.”

“He’s already hedging his bets, because he’s used to buying politicians,” Paul said. (Trump later acknowledged he gave money to the Clintons and demanded Hillary Clinton “be at my wedding” in exchange; he called this a sign of a broken system.)

Trump also stood firm on his vow to build a wall along the U.S.-Mexico border. “If it weren’t for me, you wouldn’t even be talking about illegal immigration,” Trump said, blasting “stupid leaders” in the U.S. harboring illegal immigrants.

Bush said a comprehensive solution is needed, including a “path to earned legal status,” which he said is not “amnesty.”

Moments later, Cruz said some on stage support “amnesty”, while he does not.

A big question going into the debate was whether Bush would aggressively challenge Trump and try to knock him off his perch.

But he would only go so far as to question Trump’s tone, calling his language “divisive.” Hours before the debate, Politico ran a story saying Bush recently told a donor he thinks Trump is a “buffoon” and a “clown.” Asked about that report on stage, Bush denied it.

“It’s not true,” Bush said.

Trump then called Bush a “true gentleman.”

As for his tone, Trump said it’s “medieval times” in the Middle East, and, “We don’t have time for tone.”

But other candidates were able to stand out on the crowded stage. Carson called Hillary Clinton the “epitome” of the progressive movement.

“She counts on the fact that people are uninformed. The Alinsky model, taking advantage of useful idiots,” he said.

Walker also blasted the Iran nuclear deal, as did other candidates: “This is not just bad with Iran, this is bad with ISIS, it is tied together and once and for all we need a leader who is going to do something about it. It is yet another example of the failed foreign policy of the Obama-Clinton doctrine.”

Florida Sen. Marco Rubio landed laughs when, upon being asked about his faith in God, he said: “I think God has blessed us, he’s blessed the Republican Party with some very good candidates. The Democrats can’t even find one.”

Rubio also vowed to repeal and replace ObamaCare, and called the lack of accountability after the Veterans Affairs scandal “outrageous.”  

Former Arkansas Gov. Mike Huckabee vowed to defend entitlements and stood his ground on social issues. He blasted Planned Parenthood and defended his pro-life views, accusing abortion providers of “selling” fetal parts “like they’re parts to a Buick.”

Kasich, like Walker and Bush, tried to keep the focus on his record in his state.

“America is a miracle country and we have to restore the sense that the miracle will apply to you,” he said.

And Cruz vowed, if elected, to prosecute Planned Parenthood, cancel the Iran nuclear deal and nix Obama’s executive orders. “I believe the American people are looking for someone to speak the truth,” he said.

Trump was challenged several times on his conservative views. He previously was pro-choice, but said he’s “evolved” on the issue.

Also, under questioning from moderator Megyn Kelly about past disparaging comments he made about women, Trump interrupted to say, “Only Rosie O’Donnell.” He then said, “Honestly, Megyn, if you don’t like it, I’m sorry.”

The candidates squared off at the second of two kick-off debates, hosted by Fox News and Facebook in conjunction with the Ohio Republican Party.

The seven other Republican hopefuls spent much of the first debate doing their best to hammer home the message that Clinton represents four more years of Obama. In the earlier debate, the candidates largely avoided sparring with each other and instead trained their fire on the Obama years -- with promises to roll back ObamaCare and undo the Iran nuclear deal.

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