The chief of staff to former senator David Leyonhjelm is taking over his job in Canberra.
Duncan Spender, who founded the Liberal Democrats, is filling the federal upper house seat after his old boss stepped down to contest the NSW state election.
Mr Spender said he would vote consistently with the record of his former boss when he sits in the Senate for the two remaining sitting days before the election.
"The Liberal Democrats are fighting to take over the world and leave you alone," he said in a statement on Thursday.
"The Liberal Democrats will cut taxes to get the government out of your wallet and end the nanny state so you can go about your business and live your life in peace."
He will be sworn in when the Senate next meets on April 2, before seeking re-election at the May poll.
