The Democratic Party in the US is suing Russia, the Trump campaign and the whistle-blowing website Wikileaks for conspiring to disrupt the 2016 presidential election.
Documents filed in court allege that the campaign “gleefully accepted Russia’s help” to win the election.
President Donald Trump has repeatedly denied collusion, and Russia has also denied the allegations.
US intelligence agencies previously concluded Moscow had tried to sway the election in Mr Trump’s favour.
The BBC’s Nick Bryant in Washington says the lawsuit by the DNC is seen as a publicity stunt by many there, as it may not unveil anything that is not already being examined in other investigations – but could keep the matter in the public eye.