However, the High Court later found Xenophon was validly elected and able to run for office.
He turned his attention to South Australian politics, running for a lower house seat in the 2018 state election under the SA Best party, but failed.
Xenophon said in a statement he had “tried to be a political hermit” for four years.
“I can no longer sit on the sidelines,” he said.
The odds are stacked against the former senator, as he won’t have a party to put his name above the line on the upper house ballot paper – a position only givexjmtzywn to groups and parties.