You can tell it’s the silly season when Bronwyn Bishop is in the headlines. But if you can get past that, it’s worth having a read of the story on the Libs in The Australian by my friend and former colleague Christian Kerr on optional preferential voting.

The theme is that “senior Liberals” (of whom only Bishop is named) are keen to move to optional preferences at the federal level if the Coalition wins this year’s election. It’s not seriously disputed that such a move, at least in the short term, would work in the Coalition’s favour, since the most significant preference flow these days is from the Greens to Labor.

Kerr gives some of the historical background; for a fuller discussion read what I wrote a couple of years ago on the subject. Antony Green also goes into it regularly — there was a typically sensible piece by him from 2011 — and Peter Brent today adds some further thoughts.

The key point, it seems to me, is that “political parties are captive to their histories”. For the last 30 years, preferences have helped the ALP more than they’ve hurt it; there’s barely a Liberal MP still serving who was around when their party received a net gain from compulsory preferences. Yet optional preferential voting was still branded as a Labor trick, and despite ample opportunity no Coalition government, state or federal, ever made the move.

If Kerr is right, that may now be changing. But it will encounter a good deal of institutional resistance.

The most serious problem, which every discussion of the subject comes back to, is the Liberals’ relationship with the National Party. As I put it in 2010, change “puts a loaded gun in the hands of a recalcitrant Coalition partner”. While under compulsory preferences the Coalition parties can contest each other’s seats with relative impunity (indeed that’s basically why they were introduced in the first place), optional preferences make any such contest a risky exercise.

“Opponents of change within the Coalition can also point out, quite rightly, that the longer term effects would be uncertain.”

Moreover, the more well-entrenched optional preferences become, the more serious that problem is; voters get used to just putting a “1” on their ballot paper and it takes more and more of an effort to get them to allocate preferences. State elections in New South Wales, which has the longest experience with optional preferences, illustrate the point: it’s almost unheard of for a party that trails on primaries to win a seat (the Greens managed it last time in Balmain, but only just).

So the National Party, insecure now even in its heartland seats, will take a lot of persuading. It’s not surprising to find Barnaby Joyce defending compulsory preferences, particularly with Bob Katter’s outfit now snapping at his right flank.

Opponents of change within the Coalition can also point out, quite rightly, that the longer term effects would be uncertain. Electoral systems change electoral behaviour; you can’t just look at the voting figures under one system and assume they would hold under a different system. A shift to optional preferences might, for example, be just the thing to push Labor and the Greens to closer co-operation in an effort to avoid wasting votes — presumably not the result an Abbott government would want.

That in turn raises the question of whether, if the Coalition did push for change, the Greens might be willing to provide the necessary votes to get it through the Senate. For them it would offer risks as well as opportunity — a wider set of options in allocating preferences might give them more leverage in negotiations. They might even be able to extract some sort of quid pro quo from the Coalition, such as the abolition of ticket preferencing in the Senate.

If there’s a constant theme in the history of electoral law in Australia (and most other countries as well), it’s that change is driven by perceived political interest, not by principle. Shifts to more democratic outcomes happen when a major party thinks that they will work to its advantage – as, for example, with the introduction of PR for the Senate by the Chifley government.

It’s just possible that this might be one of those cases. Whatever the politics of it, it’s hard to see any reason in principle why people should have to express preferences that they don’t hold.