[1] The trigger for the by-election was the 23 October parliamentary resignation of Joe Hockey, the backbench Liberal Member for North Sydney and former Abbott Coalition government Treasurer.

[4][better source needed][5][better source needed] Ian Macfarlane attempted to defect from the Liberal party room to the National party room with accompanying demands for additional Nationals cabinet representation, and the Mal Brough / James Ashby diary controversy deepened in the last week of the campaign.

[1] The campaign began amid claims of "widespread discontent for the Liberal pre-selection factional fix of Trent Zimmerman" and in the absence of a Labor candidate.

Despite having no financial or campaign support and facing veteran Liberal incumbent Jillian Skinner and a Labor candidate in the overlapping state seat of North Shore, Ruff won more than 10 percent of the vote.

[13] Leaked emails show potential voters were sent registration forms at 7:30 pm on a Thursday and asked to signal their availability, with the cut-off for replying by noon the next day.

[15][16] Mack also claimed that much of the electorate was angered that Hockey, who had written the "age of entitlement" speech, had forced a $1-million by-election within a year of the 2016 federal election, with the expectation of becoming the next Ambassador of Australia to the United States.

This was only the second time in North Sydney's history that the successful Liberal candidate did not obtain a majority of the primary vote and had to rely on preferences.

Zimmerman faced a double-digit primary vote swing − more than triple that of the 2015 Canning by-election − despite the absence of a Labor candidate.