Donald Trump used the final presidential debate with Hillary Clinton to declare he would keep the country “in suspense” over whether he would accept the outcome of November’s election, stoking conspiracies over the legitimacy of the democratic process.

The Republican nominee’s refusal to endorse the results of the forthcoming election, unheard of in modern American history, capped a fractious debate in which he clashed with Clinton over abortion, gun rights, immigration and foreign policy.

In some of the most heated exchanges, Clinton accused Trump of being “a puppet” of Russian president Vladimir Putin. Trump repeatedly interrupted his Democratic rival, at one point cutting her off mid-sentence with the line: “Such a nasty woman”.

However, it was Trump’s refusal to accept the outcome of an election he is currently projected to lose that will stand out from Wednesday night’s ill-tempered clash.

Trump’s comments directly contradicted those of his running-mate, Mike Pence, who just four days ago said he would “absolutely accept the result of the election”.

It also contradicted a promise Trump himself made last month, in the first presidential debate, when he was asked a near-identical question about whether he would accept the election result.

“The answer is: if she wins, I will absolutely support her,” he answered then.

However, on Wednesday Trump repeatedly refused to accept the election result and raised questions about voter registration inaccuracies.

“I will look at it at the time,” Trump said, when pressed by Fox News moderator Chris Wallace, who said Trump was breaking with centuries of peaceful transitions of power. “I will keep you in suspense, okay?” the businessman said.

Clinton described her rival’s refusal to accept the outcome of the election, which takes place in less than three weeks, as “horrifying”.

“He is denigrating and he is is talking down our democracy,” said the former secretary of state. “And I, for one, am appalled that someone who is the nominee of one of two major parties would take that position.”

“Every time Donald thinks things are not going in his direction, he claims whatever it is, is rigged against him,” said Clinton, adding that he has, at various times, accused the FBI, Republican primary process and judicial system of being corrupt.

“There was even a time when he didn’t get an Emmy for his TV programme three years in a row and he started tweeting that the Emmys were rigged.”

“Should have gotten it!” Trump interjected.

People in the debate auditorium giggled at that interruption from the Republican nominee, one of several occasions when the audience could be heard breaking a rule that they should stay silent.

On another, there were sniggers when Trump insisted: “Nobody has more respect for women that I do, nobody.”

The businessman’s treatment of women was once again on trial in a debate.

Asked about the nine women who have come forward to accuse Trump of the sexually predatory behaviour he bragged about in a 2005 video leaked earlier this month, Trump insisted they were all either seeking “10 minutes of fame” or had been somehow orchestrated by Clinton’s campaign.

“Those stories are all totally false – I have to say that,” Trump said. “And I didn’t even apologize to my wife who is sitting right here because I didn’t do anything.”

Pointing out how Trump has publicly denigrated his accusers, Clinton said: “Donald thinks belittling women makes him bigger. He goes after their dignity, their self-worth, and I don’t think there is a woman anywhere doesn’t know what that feels like.”

One of the women to level accusations at Trump, Jill Harth, who gave an extensive interview to Guardian US, tweeted mid-debate: “Trump lied and lied again,” adding: “He says he doesn’t know any of the women. Well, he definitely knew me.”

Another exchange from Trump likely to alienate some women, but one seemingly intended to court the evangelical, stemmed from a discussion about the future shape of the US supreme court, which has had an unfilled vacancy since conservative Antonin Scalia’s death in February.

Trump portrayed himself as a candidate who would protect the second amendment right to keep and bear arms and said Roe v Wade, the historic ruling in 1973 that legalized abortion in the US, would “automatically” be overturned if he were elected because of his commitment to pro-life justices.

The Republican characterized Clinton’s position as one that would “rip the baby out of the womb of the mother” just days before a pregnancy. “You can say that that is OK and Hillary can say that that is OK, but it’s not OK with me.”

Clinton countered that Trump’s “scare rhetoric is just terribly unfortunate”, while setting out her view in favour of women’s reproductive rights. “I can tell you the government has no business in the decisions that women make with their families in accordance with their rights,” she said.

The third debate was not as one-sided as the opening televised contest between the two candidates, in which Clinton was by most accounts declared the winner. Neither was it as personal as the second debate, in which the candidates clashed in some of the most brutal exchanges ever seen on a presidential stage.

However, there was nothing in the last debate that seemed likely to alter the dynamics of a race in which Clinton has a six-point lead in an average of national polls – and an edge in almost all of the key battleground states needed to win the White House.

A CNN/ORC poll of debate watchers found 52% who thought Clinton emerged the victor, compared to 39% who said Trump won.

Embarrassingly for Trump, who has claimed victory in the wake of previous debates because he “won” instant – easily rigged – online polls, he was also declared the loser on an online survey conducted by the pro-Trump website

The bad blood between the candidates was unmistakeable throughout their final head-to-head; pointedly, there was no handshake before or after the contest.