US President Joe Biden has warned any candidates who refuse to accept defeat in next week’s midterm elections could set the nation on “the path to chaos”.
He also urged Americans to unite in opposition to “political violence” in the vote on 8 November.
Mr Biden, a Democrat, said former President Donald Trump and his supporters were peddling “lies of conspiracy and malice”.
Republicans hit back that Mr Biden was seeking to “divide and deflect”.
Control of both chambers of Congress and key state governorships are hanging in the balance in next week’s elections.
Most forecasts suggest Republicans will win control of the House of Representatives, while the Senate could go either way.
Mr Biden spoke in nationally televised remarks on Wednesday evening at Washington DC’s Union Station – just a few streets from where Trump supporters stormed the US Capitol last year in an attempt to overturn the results of the 2020 election.
