Labor has launched its bid to win the Sydney seat of Bennelong with leader Bill Shorten throwing his weight behind high-profile candidate Kristina Keneally.
Mr Shorten urged voters to send a message to Prime Minister Malcolm Turnbull that Australians have had enough of his government.
"We know here that the time is nearly up for Turnbull and five years of incompetent, out-of-touch Liberal government in this nation," Mr Shorten said at Sunday's campaign launch.
"Send a message about the incompetence and the division and the policy paralysis that is the trademark of the Turnbull government."
Mr Shorten skipped Queensland Labor's election launch on Sunday in favour of the Bennelong event.
The December 16 by-election is the second brought on by the dual citizenship issue, but it's the only one Labor has a shot - no matter how long - of winning.
Liberal incumbent John Alexander was also expected to comfortably retain Bennelong on a near 10 per cent margin until the former NSW premier was parachuted in.
A Galaxy Research poll published on Saturday showed the contest will be a tight race, with Labor boasting a 10 per cent swing on a primary vote basis, up to 39 per cent against the Liberal Party's 42 per cent.
Deputy Prime Minister Barnaby Joyce faces a by-election in New England on December 2, but his margin is considered unassailable.