Los Angeles: George Papadopoulos, a former Trump campaign aide who has forged a second life spreading conspiracy theories about former Australian high commissioner to London Alexander Downer is running for Congress.

The US House California seat was left vacant by Democrat Katie Hill this week.

George Papadopoulos, former campaign adviser for US President Donald Trump. Credit:Bloomberg

Papadopoulos, who pleaded guilty to lying to the FBI in 2017, filed paperwork on Tuesday with the Federal Election Commission.

He was a key figure in the FBI's Russia probe into ties between Russia and the Trump campaign.