Nationals leader Michael McCormack says it is up to Barnaby Joyce's local branch to decide if they want to keep him in politics.
The former deputy prime minister has taken two weeks sick leave after recording a tell-all, $150,000 interview with his staffer-turned-partner Vikki Campion.
Mr McCormack told Michelle Grattan's The Conversation podcast it was up to Mr Joyce and his electorate whether he stayed in politics.
"That'll be a matter for him and that'll be a matter for the National party in New England," Mr McCormack said.
"That'll be a matter for a branch to nominate him and then that'll be a matter for the branch members in New England as to whether or not they decide if he nominates or if anybody else nominates."
He raised the example of Liberal Assistant Minister Jane Prentice, who lost her own preselection despite being a sitting MP.
"That's democracy at work," Mr McCormack said.
But former prime minister Tony Abbott, who had Mr Joyce as his deputy prime minister, backed him to stay in politics.
"He saved the government at the last election. If the National party had not won seats ... we wouldn't be in government," Mr Abbott told 2GB radio.
"Barnaby has done a lot for us in the past and I hope he will do a lot for us in the future."
Mr Joyce and Ms Campion's interview will be broadcast on Sunday night.
Mr Joyce jumped to the back bench after his relationship with Ms Campion became public in February. Their son Sebastian was born on April 16.
He has split from his wife Natalie, the mother of his four daughters.