Following the Queensland election result and yet another downturn for federal Labor in the polls, there has been talk lately about the likely make-up of the Senate should the Coalition win next year’s election in a landslide, and the potential for such a result to upset long-held assumptions about the political calculus under an Abbott government.

The dynamics of the current Parliament have always made a double dissolution all but impossible, and the prospect of a crisis-induced early election for the House of Representatives only is now looking scarcely more likely.

That leaves us looking at a conventional timetable in which the timing is effectively constrained by the need for a half-Senate election to be held no earlier than the middle of next year.

The window for a normal election is thus between August 3 — the earliest conceivable date for a half-Senate election — and November 30, the last possible date for a House of Representatives election.

As well as a new House of Representatives, such an election will determine the replacements for the 36 state Senators who were elected when Labor came to power in 2007, who will take their seats in the middle of 2014 (together with the two Senators each from the Australian Capital Territory and the Northern Territory, whose terms are tied to the House of Representatives).

The Senators elected in 2010 will continue their six-year terms in the new parliament, and the conventional view has been that their partisan composition will present an obstacle for an Abbott government determined to unpick the present government’s legislative agenda.

In such an environment, a Coalition government would have the option of pulling the rug from under the Senate by holding an early double dissolution election.

However, that might not be necessary if the election result looks anything like the current polling numbers.

The easiest way to unpick the complexities of the Senate electoral system is to group the various competing parties into right and left, however much that might offend ideological purists of either stripe.

There remains the occasional unclassifiable such as Nick Xenophon, who is up for re-election in South Australia and presumably likely to win, and potentially even Julian Assange, of whose aspirations we have heard nothing further.

In most circumstances, political parties, be they major or minor, order their preferences to favour those on their own side of the ideological divide, barring the odd significant exception like the Coalition putting One Nation last or the deal between Labor and Family First, which famously delivered Steve Fielding a Victorian Senate seat in 2004.

At half-Senate elections, results in any given state usually split three-left and three-right, with the territories’ two seats never once having failed to go one Labor and one Coalition.

However, four-and-two results have not been unknown, usually when Labor has won three seats and the Coalition two, with the last seat going to the Greens or the Democrats.

Since the 1990 election — the first at which each state returned six Senators — the only four-right, two-left results have been at the 2004 election, at which Queensland (four Coalition and two Labor) and to a lesser extent Victoria (three Coalition, two Labor, one Family First) helped deliver John Howard control of the Senate.

The difficulty for the Coalition in the next parliament is that the 2010 election produced a four-left, two-right result in Tasmania (three Labor, two Liberal and one Greens).

However, in the current environment it is very easy to envision this being counterbalanced at the next election by a four-right, two-left result in Queensland, either through a repeat of 2004 or, perhaps, a Katter’s Australian Party Senator joining three from the LNP.

In the event of three-three results in the other states, this would leave the left with 38 seats and the right with 37 (including the thus-far low-profile John Madigan of the DLP, whose election to a Victorian Senate seat in 2010 you have probably forgotten about), plus Xenophon.

Even on occasions when Xenophon voted with the right, that would still leave the left with a blocking majority, given that tied votes are resolved in the negative, and the President of the Senate unlike the Speaker of the House has a normal deliberative vote rather than just a casting vote.

To overcome this, further four-two results would be required in other states, the most likely candidates being New South Wales and Western Australia.

Assuming no cross-ideological preference deals such as the aforementioned Labor-Family First effort from 2004, a rough benchmark here is that the combined Labor and Greens vote would need to fall to about 40%. Otherwise those two parties, mutually exchanging their preferences, can collectively achieve three quotas (42.9% of the vote) with the preferences of left-wing micro-parties and independents.

At the 2010 election, the Labor-plus-Greens vote for the Senate was 42.2% in Queensland, 43.7% in Western Australia and 47.2% in New South Wales. When the Liberals and Nationals collectively succeeded in winning four seats in Queensland in 2004, it was 37.0%.

The recent Newspoll breakdowns had Labor plus the Greens at 39% in Queensland, 41% in Western Australia and 42% in New South Wales. This was in the context of figures that produced a national two-party preferred result of 54-46 to the Coalition, whereas more recent polling has had it at 56-44 or 57-43.

Four-right and two-left results in any two out of three of Queensland, Western Australia and New South Wales would very likely enable a Coalition government to repeal the carbon tax, given the likely support of Xenophon.

Such results in all three states would put a Coalition government in a fairly comfortable position similar to that of its state counterpart in New South Wales, where Labor and the Greens can be overruled in the upper house with the support of the Shooters Party and the Christian Democratic Party.