Former coalition senator Sam McMahon will contest next month's federal election for the Liberal Democrat party in the Northern Territory.
Ms McMahon resigned from the Country Liberal Party in January after losing a fierce preselection battle to Jacinta Price last year.
"I've had a fair beating from politics. I was happy to step away. I did not want to continue on in politics," she told reporters in Darwin on Friday.
"But I have exercised my female prerogative to change my mind ... I am here to announce that I will be contesting the next election in the Senate for the Liberal Democrat party."
Ms McMahon said the CLP was in shambles and she had joined the Liberal Democrats because of its professionalism.
She used her valedictory speech in parliament last week to call out allegations of bullying in her former party, saying her resignation wasn't connected to losing preselection.
"My (decision) to resign was driven entirely by my former staff member ... who abused and terrorised my office - including myself - and the party's decision to place him into a position on their central council," she told federal parliament.
Deputy Prime Minister Barnaby Joyce said he respected Ms McMahon's decision but he didn't agree with it.
"I absolutely love the fact that we're in a democracy. I love the fact that people can say what they like. I love the fact that we don't have someone with their foot on our throat subjugating us. I really like that," he said.
Ms McMahon also said on Friday that she hadn't accomplished everything she'd set out to do for the territory in politics, citing euthanasia and improving the use of federal infrastructure spending in the territory as issues she would focus on if re-elected.
She was joined at the news conference by ex-CLP candidate Kylie Bonanni, who announced she would run in the lower house seat of Solomon for the Liberal Democrats.
She's one of four high-profile resignations from the CLP in recent weeks.
The Liberal Democrats has agreed to swap preferences with Clive Palmer's United Australia Party at the election.
It will also be hoping that former Queensland premier Campbell Newman can win a Senate seat in his home state.
The party says it stands for individual liberty, free markets, small government, with limited government spending and regulation, and low taxation.
"Australia is in peril," the party says on its webpage.
"The national trial we face is caused by a failure of political leadership - our state and federal leaders from both major parties have proven themselves inept."
