Trump centre stage in debate, but can he hold the limelight?

“Authenticity”. That’s the magic ingredient, the sprinkling of gold dust, that every pol’ needs in this age of disillusionment with politics and politicians. Though what it means, I’m not sure, a bit of whatever you’re having yourself.

Jeremy Corbyn, the shock leader of the race to lead British Labour, has it apparently. A touch of the outsider – though he's been in the Commons since 1983 – he also has sincerity. He is apparently cut from a different cloth than the new Labour/new Tory clones who dominated the recent election. Bernie Sanders, the veteran socialist who is doing remarkably well in taking on Hillary Clinton for the Democratic nomination, has something of it too, according to the pundits.

And then there's Donald Trump. I heard Jon Huntsman, the former governor of Utah and one-time Republican presidential hopeful, on the BBC's Newsnight the other night extolling the billionaire property developer who has ensconced himself, to the bewilderment of all, at the front of the 17 candidates in the Republican nomination race. He is at 23 per cent in the polls, no less, double his nearest rival, the likely candidate of the party establishment, Jeb Bush. Authenticity, says Huntsman. Authentic horse**it, I would be tempted to reply.

Trump might have an erratic record, including a past propensity for supporting Democrats, a propensity for shooting his mouth off – he has described Mexican immigrants as drug dealers and rapists, and sneered at John McCain’s torture as a Vietnam prisoner of war – and a bewildering vagueness about policy – he promised to repeal Obama’s health care plan and replace it with “something terrific” .

But, Huntsman insisted, his authenticity spoke to the malaise in the Republican ranks, to that sense that even authentic Tea Party candidates from within politics had sold the pass.

And so, watching the Fox TV presidential debate on Thursday night was de rigeur for US politics nerds. No surprises. Trump was Trump, hogging centre stage, unvarnished, unprepared, unapologetic to cheers from the audience about his lack of political correctness, reiterating his slanders against the Mexican people, almost delighting in his ignorance of world affairs and the details of policy. Adept as the best politician at not answering the questions asked of him, except one – he had no problem refusing to rule out running as an independent. Ironically that sole break with bombastic obfuscation may be the one thing that hurts him with Republicans who value loyalty.

As David Brooks of the New York Times has observed, "ego is his ideology, and in this he is absolutely consistent. In the Trump mind the world is not divided into right and left. Instead there are winners and losers. Society is led by losers, who scorn and disrespect the people who are actually the winners." Ego and anger, the essence of Trump.

It makes debating with him almost impossible, as the other candidates found. Jeb Bush's lone attempt to point out his unelectability was brushed aside. Complaints about his "tone" were dismissed as irrelevant – what America needs is a man of action. And as one of his rivals, Ohio's John Kasich, admitted ruefully "Donald Trump is hitting a nerve."

But in truth the debate left the contest much as it had been – despite the hype, polls show that such debates rarely shake up the field. It may, however, have an impact on what political observers call “the invisible primary”, the contest for the hearts and minds of big donors and party insiders, most notably the hundreds of elected officials up and down the country whose endorsement later in the campaign may help secure particular slices of the vote.

The "invisible primary" now is all about who can beat Donald Trump, a candidate seen as unelectable. And as Dan Balz of the Washington Post argues, "The evening showed that the Republicans have a field of candidates potentially capable of stopping him".

Whether they can at the same time provide a serious challenge to Hillary Clinton is another matter. The Republican Party rank and file remains resolutely oblivious to the lessons of Obama's two victories – US elections are won from the centre, not by the ideological darlings of the right or left.

One Republican political commentator, Bruce Bartlett, a former Reagan appointee, last week wrote that he hoped Donald Trump becomes the party’s presidential nominee, riding the Tea Party wave, and is so badly defeated in the national election that the party has to return to the centre-right.

“I think many Republican leaders have had deep misgivings about the Tea Party since the beginning, but the short-term benefits were too great to resist. A Trump rout is Republican moderates’ best chance to take back the GOP.” On the left we call that “revolutionary defeatism”.

Trump has defied political gravity to seize the front of the Republican field. Polls show he has a strong appeal across the party demographic and political spectrum, and so the expectation that he may go the way of other shooting stars who briefly led the field in 2011 then to fade spectacularly – Michelle Bachman, Rick Perry , Herman Cain, who they? – may well be wishful thinking.

But, as John Cassidy of the New Yorker notes, polls are also showing potentially fatal flaws in his candidacy. Quinnipiac University's polling unit late last week, found that while 50 per cent of Republicans have a favourable opinion of him, and 33 per cent a negative opinion, if you subtract the latter figure from the former one, you get a "net positive" rating of only 17 per cent. "Far from placing Trump at the front of the GOP field, this figure suggests that he is in 13th place, sandwiched between John Kasich and Chris Christie. "

As the field thins Trump may well find it very difficult to draw the second preferences to his banner. The next week should also see if the name recognition bonus he has benefited from in polls so far begins to fade. Authentic or not.