Political instability is not new to Australia. Not even in the modern era, which dates from the beginning of World War II.

Sure, Australia has had five prime ministers since Melbourne Cup Day 2007 — namely, John Howard, Kevin Rudd, Julia Gillard, Rudd (again), Tony Abbott and Malcolm Turnbull. That’s six prime ministerships in six years.

However, Australia had six prime ministers in the nine years ­between New Year’s Day 1966 and Armistice Day 1975: Robert Menzies, Harold Holt, John Gorton, William McMahon, Gough Whitlam and Malcolm Fraser.

Holt had a big victory in 1966 but died in office. Gorton had a narrow win in 1969 but he was ­replaced in a partyroom ballot in 1970 by McMahon, who lost the 1972 election to Whitlam. Whitlam narrowly won in 1972 and again in 1974 but was defeated in a landslide by Fraser in 1975.

The Coalition’s big victory in 1975 saw Australia return to stable politics. This continued after Bob Hawke’s big victory in 1983 and Howard’s big victory in 1996.

The evidence suggests that what is seen as political instability stems from the electorate and from nervous politicians who see survival in changing leaders. Stability was a reality during the long-term governments of the Coali­tion (under Menzies, Fraser and Howard) and Labor (under Hawke).

In recent years, only two politicians have led their parties to large majorities in the houses: Rudd in 2007 and Abbott in 2013. But both were replaced inside their first term, by Gillard and Turnbull respectively. Gillard managed to stitch together a minority government in 2010 but was replaced by Rudd before the 2013 election.

And now we come to the present reality. The problems facing the Coalition stem from Turnbull’s failure to obtain a significant majority in the House of Representatives in the July 2 double-­dissolution election.

Turnbull’s promise was to win well. But the Coalition has a ­majority of one in the house and needs the support of nine out of 11 minor party and independent senators. Pauline Hanson’s One Nation and the Nick Xenophon Team were able to make use of lower quotas in the double dissolution to win four and three Senate seats respectively. This means that if either group sides with Labor and the Greens in the Senate, it can defeat government legislation.

The Turnbull government went into the past election with a significant majority in the house and a need to win the support of six out of eight senators. It emerged with a less favourable situation in both houses and facing the fact an unintended consequence of the double-dissolution strategy was the strengthening of the parties led by Xenophon and Hanson.

In view of this instability, Tuesday’s Newspoll is not all that surprising. Of course, polling needs to be assessed across a significant ­period. Even so, according to the most recent Newspoll, the ­Coalition’s primary vote under Turnbull is lower than it was when the Liberal Party replaced Abbott with Turnbull in September last year. This has led to speculation about Turnbull’s leadership, only months after the election.

In all likelihood, Turnbull will lead the Coalition to the next election scheduled in mid-2019. It’s difficult to see the Liberals bringing down a second prime minister in a partyroom ballot in less than four years. But precedent suggests that it is unwise to make predictions about the longevity of political leaders in contemporary times.

Predictions about the longevity of governments, however, can be made more readily. It was always likely that the Labor minority government created after the 2010 election would run a full term. No Labor MP was likely to cross the floor. Moreover, the ­independents (Rob Oakeshott, ­Andrew Wilkie and Tony Windsor) and the Greens MP (Adam Bandt) were always going to ­support Labor over the Coalition. Oakeshott and Windsor were ­motivated by a deep resentment of the Nationals and Wilkie and Bandt are on the left of politics.

It’s much the same today. Whatever those who are depicted as conservatives think of Turnbull, no Liberal Party or Nationals MP is likely to cross the floor in a bid to bring down the government.

It’s theoretically possible that a Coalition MP in a non-safe seat could die in office. But it is not clear that if Labor or a minor party or an independent won a seat from the Coalition in a by-election that this would result in the defeat of the government on the floor of parliament. It is not clear if the new parliamentarian and the ­existing independents would vote to replace a government in such circumstances.

In modern times, a government has been defeated only once on the floor of the house.

In 1941 two independents, Arthur Coles and Alexander Wilson, who had supported the Coalition since the 1940 election, indicated that they would move their support to Labor at least up to the next election. Consequently, Country Party (now Nationals) prime minister Arthur Fadden tendered his resignation to the governor-general and Labor’s John Curtin was sworn in as prime minister. In 1941, neither Coles nor Wilson had a vested interest in preserving the Coalition over Labor or vice versa.

Since the Prime Minister’s political discontents turn on the ­Coalition’s failure to win well on July 2, the perception of political instability in Australia is likely to remain until at least the next election. Turnbull cannot do much about this. But he can reduce the impact of political instability by making decisive decisions — whether of the affirmative or negative kind.

In an era of instability, there is little point in inviting electors to put everything “on the table”. The Prime Minister would be well ­advised to junk the table and give Labor and Greens deadlines with respect to issues such as the same-sex marriage plebiscite.

Turnbull’s task is to achieve in 2019 what he failed to win on July 2. He can do so only if he looks as strong as possible.