US Presidential candidate Republican Donald Trump said the final presidential debate in Las Vegas that if he loses the election, he might consider the outcome illegitimate because the process is rigged.

used the high-profile setting of here Wednesday night to amplify one of the most explosive charges of his candidacy:

Questioned directly as to whether he would accept the outcome should Democratic nominee Hillary Clinton prevail in the November 8 elcions, Trump stated “I will keep you in suspense”, reported The Washington Post.

Clinton called Trump’s answer “horrifying,” saying he was “talking down our democracy.”

After a sober start, the candidates shifted gears into a series of fiery exchanges over their fitness to serve as president and character traits. But over the course of the third and final debate, they delved deeper into their substantive differences than they did in the first two forums and offered a clearer contrast in the directions they would take the country, the report said.

 They drew sharp distinctions on the economy, trade, terrorism, immigration and hot-button social issues including abortion and guns.

Clinton and Trump argued over which of them would be more effective as commander-in-chief in dealing with his aggression and Russian cyber attacks. Clinton labeled Trump as Putin's “puppet” — prompting Trump to snap back, “You’re the puppet!” — while Trump charged that Putin had “outsmarted and outplayed” her when she was secretary of state.

The presidential candidates also clashed intensely about each other’s character deficiencies in an urgent move to persuade undecided voters just 20 days before Election Day and as people in many states already have begun casting ballots already.

Though Trump was clearly trying to present himself in a more presidential light than at the previous two debates, at times he could not contain his impulses to jab and insult, the report said.

As Clinton was needling Trump for not paying taxes, Trump interjected: “Such a nasty woman.”

The ill will between the two had reached such serious heights that the candidates dispensed with the traditional gesture of shaking hands, before and after the debate.