The by-election was triggered by the resignation of former state National Party leader and Deputy Premier, Peter Ryan.

Ryan had been a member of the Victorian parliament for over 22 years, and last retained the seat at the 2014 election on a 65.7 percent two-party vote, with a negative 6.9 percentage point swing.

The two-party preferred count was initially completed between the Nationals and the Greens, who the VEC predicted to finish first and second respectively.

However, Liberal candidate Scott Rossetti polled above Green Andrea Millsom and so a further distribution of preferences was required.

[4] The Greens campaigned strongly on an anti-coal seam gas platform, and encouraged voters from other parties to write "no CSG" on ballot papers to register their displeasure with the practice.