Republican White House hopefuls on Thursday unleashed withering criticism against billionaire frontrunner Donald Trump, branding him a celebrity and unprincipled flip-flopper as the party kicked off its first debate events of the 2016 campaign.

Former Texas governor Rick Perry and former Hewlett-Packard chief Carly Fiorina launched the first assaults against Trump in the opening event in Cleveland, which featured the bottom seven candidates -- according to polls -- in a 17-strong field.

With the top 10 -- Trump among them -- squaring off in the main debate at 9:00 pm (0100 GMT Friday), the anti-Trump fireworks quickly popped off in the afternoon event.

Fiorina painted Trump as a recovering Democrat who cozies up to the Clintons and has "changed his mind" on key social issues.
"I didn't get a phone call from Bill Clinton before I jumped in the race. Did any of you get a phone call from Bill Clinton? I didn't," Fiorina snapped, when asked if Trump had got the better of her in the early stages of the campaign.

Fiorina was tapping into revelations this week that Trump called the former president -- and husband of Democratic frontrunner Hillary Clinton -- near the start of his improbable campaign.

"Maybe it's because I hadn't given money to the (Clinton) foundation or donated to his wife's Senate campaign," she added, referring to reports about Trump's past support for the Democratic family.

Fiorina acknowledged the real estate mogul has risen to the top of the polls because he is tapping "into an anger that people feel" about American politics as usual.

But "since he has changed his mind on (immigration) amnesty, on health care and on abortion, I would just ask what are the principles by which he will govern?" she asked.
Perry, who had been mocked by Trump in one of the tycoon's earlier speeches, said the frontrunner, a onetime reality television star, was "using his celebrity rather than his conservatism" in the race.

"How can you run for the Republican nomination and be for single-payer health care?" Perry said, recalling Trump's comments more than a decade ago in which he expressed support for a universal health care system.

The candidates, each looking for a breakout moment that would catapult them into the top tier, also focused their ire on the Democratic frontrunner.

"She represents a third term of a failed presidency," said Senator Lindsey Graham.

"Until you change the policies of Barack Obama, we're never going to grow this economy (and) we're never going to be safe," he said.