Republican Donald Trump has refused to commit to accepting the election result if he loses, in the final TV debate against Hillary Clinton. "I will tell you at the time," he told moderator Chris Wallace. For days he has claimed the election is "rigged". The Las Vegas debate continued the campaign's bitter tone, with Mr Trump calling Mrs Clinton a "nasty woman". Polls show Mr Trump is losing in key battleground states after facing a slew of sexual assault allegations. The candidates both declined to shake hands before and after the political debate, setting the tone for another debate marked by shouting and interrupting.