Donald Trump has hailed his rally for veterans in Iowa as a "phenomenal night", saying more than $6 million (£4m) has been raised.
He said it was better than the debate where "they're all sleeping".
"Isn't that better than this debate that's going on where everyone's sleeping?" he said.
Former Florida Governor and Republican candidate Jeb Bush has described Donald Trump as a "teddy bear" after saying he missed his fellow candidate's appearance at the party's Iowa debate.
Trump decided to boycott the final Republican debate because of a row with hosts Fox News and instead is hosting his own rally elsewhere in the city.
Donald Trump told an audience in Iowa he wanted to be at the Fox News debate but he had been "treated badly".
Mr Trump is boycotting the final Republican debate because of a row with the network, but said Fox "wanted me there".
"I didn't want to be here. I wanted to be about five minutes away," he told the audience.
"You have to stick up for your rights, when you're treated badly."
He added: "We're told we have more cameras than they do by quite a bit."
Republican candidate Ted Cruz has kicked off tonight's Iowa debate by mocking his opponent Donald Trump and suggesting he has shown a lack of respect to voters by not showing up.
"I'm a maniac and everyone on this stage is stupid fat and ugly and Ben you're a terrible surgeon.
Now we've got the Donald Trump portion out of the way I want to thank everyone here for showing the men and women of Iowa the respect to show up.
Donald Trump's foundation has raised more than $5 million (£3.5m) for veterans ahead of a rally he is holding during the Republican debate in Iowa.
Ahead of Thursday night's event, the billionaire said he would be donating $1m of his own money to the fund and that many of his wealthy friends would also be contributing.
Trump launched a website, donaldtrumpforvets.com, collecting donations for the cause on Thursday.
He is boycotting the final GOP debate because of a feud with host Fox News.
US Republican party presidential candidates are preparing for a key debate in Iowa this evening which is going ahead despite current front-runner Donald Trump's refusal to attend.
Texas Senator Ted Cruz, Florida Senator Marco Rubio, former Florida Governor Jeb Bush, New Jersey Governor Chris Christie, Ohio Governor John Kasich, Kentucky Senator Rand Paul and retired neurosurgeon Ben Carson will all take part in the debate.
Trump has opted out of the chance to take part instead choosing to host his own event nearby.
Donald Trump threatens to withdraw £700m Scottish investment if banned from UKRead the full story ›
President Barack Obama has conceded that the Republican party has had a "good night" after they secured a majority in the US Senate in last night's midterm elections.
He said that the message from last night was that voters want to see the Washington gridlock eased.
Watch Obama's press conference at the White House: