If by some chance a referendum on four-year terms were held, one of the rallying cries of its opponents would be the offensiveness of giving eight-year terms to the party hacks who populate the Senate. Hawke’s 1988 referendum tried to meet that by abolishing rotation in the Senate, giving them all four-year terms as well, but that didn’t capture the public imagination either.

This is a topic that’s easy to get confused about, despite the careful research of people like Scott Bennett, so it’s worth going through it carefully.

Currently the House of Representatives has flexible three-year terms, but the Senate has fixed six-year terms (ignoring double dissolutions). So if Reps elections are held too early, the two get out of alignment and separate half-Senate elections have to be held, as happened in 1953 and again in 1964, 1967 and 1970.

Separate half-Senate elections are expensive and inconvenient, but more significantly they are bad for the government of the day because voters can treat them like giant by-elections, giving those in power a kick without putting in the opposition. Governments have therefore avoided them for the last 30 years and will continue to do so.

As long as the taboo on separate half-Senate elections holds, we have a sort of semi-fixed term for the lower house as well (unless double dissolutions are contrived). To gain more flexibility, governments have tried to abolish fixed terms for the Senate: this is the proposal misleadingly called “simultaneous elections” that was defeated by referendum in 1974, 1977 and 1984, and was also part of the 1988 Hawke referendum.

If there’s a referendum for flexible four-year terms, this will come up again; as Glen Milne said yesterday, “The Senate would have a maximum eight-year term” – maximum, not fixed. But that means we would move further away from fixed terms, since governments could manipulate election dates free from any concern about getting out of alignment with the Senate.

Even Bennett has trouble with this, referring in two of his options (B and D) to “eight-year fixed” terms for the Senate together with simultaneous elections, although his text makes it clear that in fact that means flexible Senate terms. If we can learn anything from referendum results, however, we know that flexible Senate terms are a non-starter.

Australia’s history of failed constitutional amendment can be summed up in one sentence: politicians always want more power, but voters don’t want to give it to them.