Even in boycotting a debate with his Republican rivals, front runner Donald Trump managed to upstage them on 28 January with a typical dramatic flourish. Instead of attending a seventh debate, the former reality TV star held a competing event across town that he said raised $6m (£4m) for US military veterans. In doing so, he cast a shadow over his rivals, who frequently tossed barbs his way.

Trump's refusal to participate in the debate out of anger that Fox News anchor Megyn Kelly was a moderator prompted a flurry of last-minute phone calls with Fox News Chairman Roger Ailes that failed to resolve their dispute. A Fox News statement said Trump requested that Fox contribute $5m to his charities in exchange for his attendance, which the network turned down.

"Before we get to the issues, let's address the elephant not in the room tonight," said Kelly as she opened the debate alongside two other moderators. "Donald Trump has chosen not to attend this evening's presidential debate. What message do you think that sends to the voters of Iowa?"

In his response, Senator Ted Cruz from Texas mocked the Republican front runner. "I'm a maniac and everyone on this stage is stupid, fat and ugly, and Ben, you're a terrible surgeon," he told his rivals, including Ben Carson, a retired neurosurgeon. Cruz's next sentence began: "Now that we've gotten the Donald Trump portion out of the way."

US election 2016: Who are the main Republican candidates? IBTimes UK

"I kind of miss Donald Trump. He was a little teddy bear to me," joked former Florida governor, Jeb Bush. "We always had such a loving relationship during these debates."

But Senator Marco Rubio from Florida, a top challenger to Trump in Iowa, along with Cruz, seemed keen to move the conversation away from the absent candidate. "Let's begin by being clear what this campaign is about. It's not about Donald Trump. He's an entertaining guy; he's the greatest show on earth," he said. "This campaign is about the greatest country in the world and a president who has systematically destroyed many of the things that made America special."

The Iowa caucuses kick off on 1 February, followed by the first-in-the-nation primary in New Hampshire on 9 February.