The year began with a filing cabinet full of sensitive government documents being sold in a Canberra second-hand store.

Then in August, a cabinet full of insensitive government ministers sold out a prime minister.

A swag of seven by-elections - which began with Labor's David Feeney quitting in February over his citizenship status - ended in the government collapsing into a minority in the final weeks of the parliamentary year.

Along the way, the Liberals retained government in Tasmania and ousted a 16-year-old Labor government in South Australia.

And Labor comfortably held power in Victoria in November, amid a fractious Liberal Party in Canberra and a lacklustre state campaign.

The first major hurdle of the year for the coalition government was the revelation in the Daily Telegraph in February that deputy prime minister and Nationals leader Barnaby Joyce's former media adviser Vikki Campion was pregnant with his child.

Then prime minister Malcolm Turnbull, who instituted the so-called ministerial "bonk ban", put conservatives in his team offside by calling it a "shocking error of judgment" by Mr Joyce.

Mr Joyce hit back describing the prime minister's comments as "inept" and hurtful.

Michael McCormack stepped into the deputy PM role, leaving a rump of coalition MPs muttering among themselves about the government's leadership and direction.

Wins for the Liberals in Tasmania and South Australia - the latter ending a 16-year-old Labor government - were positive news for the government in March.

But a 30th Newspoll loss in a row - the benchmark set by Mr Turnbull for ousting Tony Abbott - brought a fresh focus to the federal Liberal leadership.

An emboldened Peter Dutton mused out loud in a series of interviews about wanting to one day become prime minister.

But keeping a lid on this was public disgruntlement over his handling of offshore detention, his militarization of the immigration system and an AAP story about him fast-tracking visas for European au pairs.

A day after the government was hopeful of a popularity boost from a positively received budget chock-full of giveaways such as personal income tax cuts, the citizenship crisis reared its head - forcing out Labor senator Katy Gallagher and bringing into question the eligibility of four lower house MPs.

While the personal income tax cuts passed parliament in June, the government was forced to shelve its much-vaunted business tax cuts after Pauline Hanson reneged on her support - losing NSW senator Brian Burston from her party in the process.

The July 28 Super Saturday of by-elections - to deal with MP eligibility issues and the retirement of Labor's Tim Hammond for family reasons - took on a national focus when Mr Turnbull framed it as a test of leadership between him and Bill Shorten.

With the Liberals failing to win any of the five by-elections, Mr Turnbull played it down.

But within a few weeks he was caving in to conservative rebels in his ranks and retreating from plans to legislate climate change targets through the National Energy Guarantee.

He won a spill on August 21 by 48 votes to 35, but was mortally wounded.

Just days later after botched number-counting by the Dutton forces, Scott Morrison accidentally became the 30th prime minister of Australia, with Josh Frydenberg defeating Greg Hunt for the deputy leadership, paving the way for his elevation to treasurer.

Mr Turnbull resigned from parliament, not wanting to be a "miserable ghost", triggering the Wentworth by-election.

The new prime minister sought to put his stamp on the government by dumping long-held plans to raise the retirement age to 70 from 67 and elevating the drought to the top national issue.

An aged care royal commission, set to start in December, pre-empted a damning Four Corners report.

A $4.6 billion peace deal was struck with Catholic and independent schools, heading off another potential election-losing issue, with more money in the kitty for an election year based on the first surplus budget in a decade.

A messy week in which Mr Morrison flagged the shifting of Australia's Israeli embassy to Jerusalem and coalition senators voted in favour of Hanson's "it's OK to be white" motion (later backtracking) saw the Liberals' Dave Sharma lose Wentworth to independent Kerryn Phelps.

Federal Liberal disunity was blamed on Daniel Andrews securing a landslide victory in the Victorian state election on November 24.

In the final fortnight of parliament for the year, the government was rocked by Julia Banks' decision to quit the Liberals and sit on the crossbench, just as Mr Morrison was seeking clear air to talk about delivering the first budget surplus in 12 years.

The minority parliament - thanks to Dr Phelps' election - suddenly became a more difficult beast to manage.

To reassert at least some semblance of authority, the prime minister secured a change to the leadership spill rules in the Liberal Party room.

He also managed to secure a win on national security laws dealing with encrypted communications, but the rest of the final parliamentary fortnight of the year was a shambles.

The resignation Nationals MP Andrew Broad from a junior ministry over a sex scandal just before Christmas topped off a horror year.

Australians are set to head to the polls five or six weeks after an April 2 budget, with government disunity - seen so clearly during 2018 - front of mind at the ballot box.

Australian Associated Press