O’Sullivan will replace Bendigo-based MP Damian Drum, who served as upper house MP for Northern Victoria before winning the federal seat of Murray last month.

The Nationals have yet to decide whether O’Sullivan will also be based in Bendigo.

The 44-year-old has worked as the chief of staff to Nationals leader Peter Walsh, served as the party’s state director, and worked as the campaign manager for Damian Drum.

The Nationals confirmed the endorsement on Sunday.

O’Sullivan, originally from Patchewollock in the Mallee but now based in Melbourne, said he was looking forward to engaging with people in the upper house seat stretching from Mildura to Wodonga.

“I’ve had good experience in policy in the parliament, but now is an opportunity to really get into the issues in regional Victoria,” he said.

“The conditions of roads in regional Victoria is an issue everyone is aggrieved about, so I will advocate for better and safer roads.

“I also have a big interest in the CFA issue. Everywhere I’ve been going, people have been distressed about Daniel Andrews’ attempt to seize control of the CFA.

“I’d like to see the current EBA abandoned and for a more palatable solution be found.”

Despite picking up an extra seat at last month’s federal election, the Nationals lost several seats in Victoria at the last state election in 2014.

O’Sullivan put the result down to re-distribution, and believed the party’s brand remained “strong” in regional Victoria.

“With every election cycle, numbers move around,” he said.

“In Murray, the Nationals primary vote doubled at the last election which saw Damian Drum elected.”

The Nationals leadership will meet in the coming weeks to decide where O’Sullivan will be based. The Department of Parliamentary Services still holds the lease over Damian Drum’s former office on Barnard Street.

O’Sullivan will remain in the role until the next state election in 2018.