New Deputy Prime Minister Michael McCormack is set to decide who will be his replacement as veterans affairs minister within days.
The new Nationals leader has taken on the infrastructure and transport portfolios, and will decide in the next couple of days who will become the nation's third veterans affairs minister since December.
Party members and senators gathered for a special party meeting on Monday to see former leader Barnaby Joyce formally stand down after weeks of fall out surrounding his marriage break-up and relationship with a former staffer who is now pregnant.
"I want to make sure that people know that in me they will have a fighter. I have a huge challenge ahead of me," Mr McCormack said after the vote.
NSW MP David Gillespie and agriculture minister and Joyce supporter David Littleproud earlier withdrew from a leadership contest.
But in a surprise move, Queensland MP George Christensen put up his hand, although his bid was unsuccessful.
Mr McCormack has previously been criticised for penning a 1993 column when he was a former newspaper editor describing homosexuality as "sordid behaviour".
He has since apologised and voted in favour of same-sex marriage in parliament.
Despite stepping down from the leadership, Mr Joyce is still under investigation over his parliamentary expenses.
Prime Minister Malcolm Turnbull on February 21 ordered a review of whether Mr Joyce broke the ministerial code of conduct, but the review was cancelled after Mr Joyce quit two days later.
The Independent Parliamentary Expenses Authority is still investigating his travel.
Mr Joyce cited allegations of sexual harassment - which he denies - as the final straw that led him to resign.
Catherine Marriott, a former West Australian Rural Woman of the Year, accused Mr Joyce of sexual harassment, but says she never intended for the allegations to go public.
Nationals federal president Larry Anthony confirmed he asked for her complaint against Mr Joyce be made in writing, but he insists he did not leak it.
"The confidentially that we were imposed on, by her solicitor and mine, we have kept," Mr Anthony told Sky News on Monday.
