And as the parliamentary fortnight wrapped up, talk in Canberra turned to whether an early election is in prospect. A poll is not due until September 2016, and could actually be held up to three months after that.

But there is growing chatter that a poll could be held by the end of the year, in November/December, or in February/March next year.

Shorten, for example, put his MPs on notice that Parliament may not return until after an election.

But Abbott says anyone who thinks a poll is just around the corner should "have a Bex and a long lie down".

But an email from his chief of staff, Peta Credlin, that offered Coalition MPs a chance for an updated photo opportunity sparked renewed speculation that, if not wide open, the door is at least ajar and a snap poll could be called.

1. History favours the incumbent

Australians typically give governments a couple of terms to settle in an do what they were elected to do. Labor's James Scullin, elected prime minister in 1929 was the last "oncer", losing power in 1931. Labor's Gough Whitlam won in 1972 and went early in 1974. Despite his government already being on the slide, Whitlam was given a second term by voters. And John Howard went early in 1998 and lost the popular vote because of a GST scare campaign, but his gamble paid off - he hung on to power and went on to win four elections in total. Abbott, a student of history, will be keenly aware that voters tend to let governments finish what they started.

2. Second budget bounce

The second Abbott-Hockey budget has provoked nothing like the vicious backlash their first budget suffered. The small business tax cuts and deductions are popular, sensible savings are being passed and as a result, the government has some of the clear air it sorely lacked last year. More importantly - as recent polls indicate - voters are having a second look at Abbott and the Coalition.

Treasuer Joe Hockey and Prime Minister Tony Abbott during budget week. Photo: Alex Ellinghausen

3. Mixed economic signals

The Australian economy is sluggish, and the data is sending mixed signals. Unemployment is expected to rise (though the numbers are bouncing around), consumer and business confidence are heading in different directions, while the IMF warned this week of over-inflated revenue and spending expectations. Against that backdrop the third Abbott-Hockey budget, due before a September 2016 election, will be under pressure. The solution? Go early, if the economy is headed south, and worry about the budget surplus after the poll.

4. PM mends fences with backbench

The Prime Minister has made serious progress in repairing relations with his backbench MPs. Credlin's email to backbenchers offering up the Prime Minister for photos would have been unthinkable a few short months ago. The offer is a clear measure of how much Abbott's standing in the party room has improved, and of returning confidence inside government. And a confident prime minister is a minister primed to go an election. Shorten, on the other hand, is facing a difficult appearance before the royal commission into trade unions next month.

Opposition Leader Bill Shorten faces an appearance before the unions royal commission in July. Photo: Alex Ellinghausen

5. Abbott, the proven campaigner

Make no mistake, Abbott believes he can beat Shorten during the campaign proper. Abbott is a proven campaigner and Shorten demonstrably lacks the ability to deliver a cut-through line (no, zingers don't count). He has told colleagues that if the Coalition is trailing in the polls 48 per cent to 52 per cent at the start of the campaign he will be able to haul in the Opposition Leader and win. He may well be right.

Tony Abbott and his daughters during the 2013 election campaign. Photo: Alex Ellinghausen

1. Double dissolution rules

As ABC psephologist Antony Green points out, the earliest a "normal" election of half the Senate and the House of Representatives can be called is August 6, 2016. That means an early poll has to be a double dissolution - and there are two potential problems with that. The first is, while the government does have a trigger - the blocked abolition of the Clean Energy Finance Corporation - it's hardly an issue to build an election campaign on. Secondly, and more to the point, a double dissolution could very likely increase the number of crossbenchers in the Senate with whom the government would need to negotiate. That's because the quota required to be elected a senator in a double dissolution is half that required in a normal half Senate election. And to date, the government has a mixed record in negotiating with the current eight member crossbench - so why would the government increase the size of its headache by growing the crossbench?

2. Voting reforms and new electoral boundaries

Senate voting reforms that would allow optional preferencing for parties above the line on the Senate voting paper are in prospect. Sounds boring, right? It isn't. In practice, the proposed changes mean that complicated preference deals that saw, for example, Ricky Muir elected with a primary vote of just 0.51 per cent could be rendered ineffective. The government will want these changes bedded down before a poll is called. If - or when - a bill appears to enact these changes, a poll will likely not be far away. In addition, the Australian Electoral Commission is re-drawing electoral boundaries in NSW, which will lose a seat, and in WA, which will gain a seat - and it isn't finished yet.

3. Those polls

While the trend is (slowly, slightly) improving the Coalition trailed Labor by 47 per cent to 53 per cent in the June Fairfax Ipsos poll. That would see the Coalition lose a notional 30 seats and government under a uniform swing. Swings are rarely uniform, elections tend to favour the incumbent and the (uneven) trend in the polls has been back to the government. But that is still an election-losing position.

4. Recent history of one-term governments

Australians are increasingly impatient with their governments. While Scullin was the last oncer, Julia Gillard went awfully close to losing in 2010. And voters in Victoria and Queensland gave former premiers Denis Napthine and Campbell Newman short shrift, booting both men out after just one term in 2014 and 2015 respectively. This will not have escaped anyone's notice.

Former Queensland premier Campbell Newman after his election loss in 2015. Photo: Glenn Hunt

5. Campaign readiness

Planning and executing a campaign takes months of work, hundreds of people and millions of dollars. None of the major parties are ready yet - though you can bet preparations are now beginning in earnest. As the PM is said on Thursday: "This is a government that was elected to govern for three years". But the iron rule of politics is that Prime Minister go when they believe they can win.

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