Former senator Nick Xenophon is making a fresh tilt for the upper house at the federal election due in May.
"I'm back, because I give a damn," the South Australian lawyer said on his campaign website launched on Thursday.
Mr Xenophon was first elected to the Senate for SA in 2007 and was re-elected in 2013 and 2016.
He resigned in October 2017 at the height of the dual citizenship scandal, after he announced he was unsure whether he was a dual citizen, which would have made him ineligible to run for parliament.
However, the High Court later found Mr Xenophon was validly elected and able to run for office.
He turned his attention to South Australian politics, running for a lower house in the 2018 state election under the SA Best party, but failed.
