The Liberal Party candidate for the seat of North Sydney, Trent Zimmerman, is expected to win Saturday's by-election comfortably.

Joe Hockey giving his valedictory speech in Federal Parliament. ( ABC: Nick Haggarty, file photo )

The by-election was triggered when former Treasurer Joe Hockey quit politics.

Mr Zimmerman, the acting president of the Liberal Party, won the preselection for the party's candidacy back in October, much to the chagrin of some within the party who described it at the time as a "stitch-up" because not all branch members of North Sydney were allowed to vote.

Mr Zimmerman said he was encouraged by the reaction from North Sydney residents.

"There's still a long time before polling booths shut so I'm out there meeting voters today and will do that right up until 6:00pm when polling booths close," he said.

Other candidates include Silvana Nero, the wife of Christian democrats MP Fred Nile, as well as candidates for the Palmer United Party as well as the Bullet Train for Australia Party.

The Labor Party is not fielding a candidate.

The Australian Electoral Commission estimates the by-election will cost around $1 million.

ABC election analyst Antony Green said the main competition for the Liberal party would be the Greens.

He said the Greens candidate, Arthur Chesterfield-Evans, was looking likely to come second, but still would not really be a challenge for the Liberals.

"The two real opponents for the Liberal Party in this contest are Arthur Chesterfield-Evans, he's a former Democrat member of the NSW Upper House and Stephen Ruff, who contested the local state seat at the general election opposed to the sale of land at Royal North Shore Hospital," Green said.

"North Sydney is a very safe Liberal seat, I mean, there's only three times in the last 60 years that the Liberals haven't won it on first preferences."

Both times the Liberals lost the seat were to Ted Mack, an independent, Green said.

He said the Greens would pick up much of the Labor vote in the contest.

Green said the way the preselection process was conducted ruffled a few feathers within the party's rank and file.

"The Liberal Party has had an internal debate going on for several years now about whether they should be using rank and file preselection ballots: that everybody who's a member in a district votes, and that's not the system the party currently uses," he said.

"The party chose the current rules to quickly adopt Mr Zimmerman as the candidate so they could hold the by-election before Christmas and get it over and done with, and also avoid any internal faction fighting."