Donald Trump casts a new, dark shadow over US election

Donald Trump came to Sin City needing to make amends with undecided voters turned off by his many past transgressions. Instead he left the third and final US presidential debate in Las Vegas unrepentant and unchanged.

Heading to Nevada behind in national polls and the battleground states that will decide the election, the New York businessman had one last chance in the third televised debate with Democratic opponent Hillary Clinton to rescue his floundering presidential bid.

But, like in the first two debates, he played to his own supporters.

They will not be enough for him to win the White House and Trump's combative, hotheaded performance last night will further alienate the college-educated whites, and female and minority voters feel he needs to turn his campaign around.

Trump called Clinton “ a liar” and “a nasty woman,” spoke graphically on abortion noting that “with Hillary you can rip the baby out of the womb of the mother just prior to the birth of the baby” and denied three times that he had try to discredit one of nine women who accused him of sexual misconduct by questioning her looks. (He did.)

The debate did not start off that way. For the first 40 minutes, it looked like Trump had suppressed his petulant streak, refusing to take the bait on a few barbs from Clinton. He was uncharacteristically calm and did not interrupt.

The discussion was at first strangely mild-mannered and substantive, appearing that it might be unlike either of their previous two encounters: a typically dull, policy-driven presidential debate. The wheels came off for Trump when Clinton challenged him on his admiration for Vladimir Putin. All it took was some name-calling, as the roles were reversed and Democrat borrowed some of Trump's own tactics to rile her opponent, interrupting and taunting him.

When the Republican suggested that Putin had no respect for her, her shot back - “well, that’s because he’d rather have a puppet as president” - left Trump scrambling with playground retorts.

Angry toddler

“No puppet, no puppet,” he said, like an angry toddler, trying to interrupt the Democratic nominee after being clearly burned by her zinger.

“You’re the puppet,” he continued. “No, you’re the puppet.”

Clinton was more free-wheeling and ready to pounce in this debate and it helped her performance. When Trump bragged about his “very beautiful” Las Vegas hotel down the street, Clinton quipped: “Made with Chinese steel.”

Even at the Republican’s nominee’s most effective moments in this debate, comparing economic achievements over 30 years in public life against the country’s beleaguered manufacturing sector as he cast himself as an agent of change, Clinton was ready with a pre-prepared putdown.

"On the day when I was in the situation room, monitoring the raid that brought Osama bin Laden to justice, he was hosting The Celebrity Apprentice so I'm happy to compare my 30 years of experience," she said.

Once again in this campaign, Clinton scored the biggest points by using Trump’s own words against him and by questioning his fitness to be president. She painted a vivid picture in the minds of the American people questioning whether Trump was not the man they want just “four minutes” from the order to the launch of nuclear weapons.

"This is just another lie," Trump said to Clinton's charge that he had said Japan should have their own nuclear weapons.

“Well, I’m just quoting you,” Clinton replied.

“There’s no quote. You’re not going to find a quote from me,” he said. (There is one.)

Through the meandering answers, incoherent half-sentences and bizarre non sequiturs, Trump was eventually on the aggressive defensive again.

Asked whether he would accept the result of the election, he retreated to his last desperate line of defence: he left open the possibility that the might challenge the result of the election.

Coming after days of warning about a “rigged” system and the possibility of a stolen election, Trump refused to say whether he would accept defeat and that he would have to wait until November 8th to decide on the outcome.

“I will tell you at the time. I will keep you in suspense,” Trump said of the moment 19 days from now.

The threat to undermine the entire American democratic process by questioning its integrity in advance - coming after his incitement of violence at rallies and stoking his angry anti-establishment supporters with claims of a “rigged” election - marks a dangerous and unprecedented turn not just in this election, but in modern US politics.

His base of supporters will love his hardline burn-it-down stand - taken from the scorched-earth strategy of the hard-right conservative Breitbart media strategists driving his campaign - but it will win over few others.

The CNN/ORC poll of debate watchers found that 23 per cent were more likely to vote for Trump after seeing him in the third debate compared with 22 per cent for Clinton, cancelling out each other’s gains. A majority, 54 per cent - the highest of the three debates - said last night did nothing to change their view.

Trump needed to move the needle and didn’t. He has left Clinton in pole position but cast a new, dark shadow over this election by questioning its legitimacy.