Republican presidential candidates lost no time in taking advantage of a rare opportunity to step out of front-runner Donald Trump's shadow in the party's last debate before the Iowa caucuses.
The policy-heavy event in Des Moines offered a glimpse of what the Republican contest might have been without the unpredictable billionaire businessman - but the candidates could not resist lampooning Mr Trump for boycotting the final debate before voting kicks off in the 2016 campaign on Monday.
Iowa residents will choose among the Republican and Democratic candidates in the first of a series of state-by-state contests to choose delegates to each party's convention.
Texas senator Ted Cruz, locked in a tight contest with Mr Trump in Iowa, opened the debate with a sarcastic impression of the property mogul's frequent insults of his opponents.
"I'm a maniac and everyone on this stage is stupid, fat and ugly," Cruz said. "And Ben (Carson), you're a terrible surgeon."
Then he thanked his fellow candidates for showing Iowa voters respect by turning up.
Former Florida governor Jeb Bush, a frequent Trump target, said: "I kind of miss Donald Trump; he was a teddy bear to me."
But, never one to go quietly, Mr Trump held a competing rally at Drake University in Des Moines, an event his campaign said was raising money for military veterans.
"When you're treated badly, you have to stick up for your rights," Mr Trump said, explaining he was skipping the debate because he felt Fox News had dealt with him unfairly.
"We have to stick up for ourselves as people and we have to stick up for our country if we're being mistreated."
Mr Trump has feuded with Fox News for months, particularly its anchor and debate moderator Megyn Kelly.
Fox News Channel said on Thursday that Mr Trump had demanded a$5m contribution to his charities in order to appear in the debate, which the network rejected.
Fox News said its chairman Roger Ailes, in conversations with Mr Trump, "acknowledged his concerns" about a statement the network had made in the days leading up to the debate.
Mr Trump's absence put the spotlight on Mr Cruz, who is challenging for the lead in Iowa, as well as on Florida senator Marco Rubio, who needs a strong showing in the state to stay competitive.
The two senators engaged in a lengthy debate on immigration, one of the most contentious issues among Republicans.
Both have been accused of shifting their stances on legalising some of those in the United States covertly, a position opposed by many party voters.
Mr Cruz accused Mr Rubio of making a "politically advantageous" decision to support a 2013 Senate bill that included a pathway to citizenship, while the Florida senator said his rival was "willing to say or do anything to get votes".
In a rare stand-out debate moment for Mr Bush, the former Florida governor sharply sided with Mr Cruz in accusing Mr Rubio of having "cut and run" on the Senate immigration bill, saying: "He cut and ran because it wasn't popular with conservatives."
With their White House hopes on the line, the candidates worked hard to cast themselves as best prepared to be commander in chief and take on terror threats emanating both from abroad and within the United States.
Mr Rubio struck an aggressive posture, pledging that as president he would go after terrorists "wherever they are. And if we capture them alive, we're sending them to Guantanamo".
He also stood by his previous calls for shutting down mosques in the US if there were indications that they were being used to radicalise Muslims.
Kentucky senator Rand Paul, back on the main debate stage after being downgraded to an undercard event because of low poll numbers earlier this month, warned against closing down mosques and also raised concerns about the US getting involved militarily in Syria, where the Islamic State (IS) group has a stronghold.
The candidates largely sidestepped direct confrontations with each other, focusing some of their most pointed attacks on Democratic front-runner Hillary Clinton.
"She is not qualified to be president of the United States," New Jersey governor Chris Christie said.
"What we need is someone on that stage who has been tested who has been through it."
Mr Trump's campaign said his Drake University rally raised more than $6m for veterans.
In a statement after the rally, it added that if Fox News "wanted to join in that effort and make a contribution, Mr Trump would have welcomed that".
Vefore the rally Mr Trump told reporters he had fielded multiple calls from Fox representatives and Mr Ailes during the day.
Fox's statement said Mr Ailes had three brief conversations with Mr Trump on Thursday about possibly appearing at the debate, but "there were not multiple calls placed by Ailes to Trump".