US Senate- Impeachment trial of former President Donald Trump is constitutional.
Former US President Donald Trump's defence team argued that he could not face trial after leaving the White House.
But a 56-44 majority voted in favour of continuing, with a handful of Republicans backing the measure.
Mr Trump is accused of "inciting insurrection" when Congress was stormed last month.
Thousands gathered in support of false claims that widespread electoral fraud denied Mr Trump victory in the US presidential election.
However Mr Trump is almost certain to be acquitted because only six Republican senators voted to move forward with impeachment, well short of the 17 Republicans whose votes would be needed to convict Mr Trump.
Democrats prosecuting the case opened the proceedings by showing a dramatic video montage of Mr Trump's 6 January speech and the deadly rioting by some of his supporters.
"That's a high crime and misdemeanour," Representative Jamie Raskin of Maryland said of the footage. "If that's not an impeachable offence, then there's no such thing."Lawyers for the former president argued it was unconstitutional to put a former president through the process at all and accused Democrats of being politically motivated.
A two-thirds majority is required to convict Mr Trump in the evenly split 100-seat Senate. Tuesday's vote implies loyalty toward the former president in his party remains high enough to avoid a conviction.
However, if convicted, Mr Trump could be barred from holding office again.