South Australian shadow minister Martin Hamilton-Smith, whom I confess I had never heard of until yesterday, seems to have made his own small piece of history by staging an unsuccessful leadership challenge.

Once upon a time, unsuccessful leadership challenges in the Liberal Party were not particularly unusual – federal leaders Snedden, Fraser and Hewson all faced them, and Jeff Kennett in Victoria faced four. But in more recent times they’ve become as scarce as hen’s teeth.

Modern dogma has it that disunity is the one unforgivable sin in a political party. But this creates a vicious circle: unsuccessful challenges, instead of being just shrugged off, are regarded as a disaster; therefore the announcement of a challenge sets off a landslide, because almost any change is seen as preferable to disunity. This means that any potential challenger has an enormously potent weapon and conformity has to be enforced all the more rigidly to prevent challengers from emerging.

The South Australian Liberals look to have escaped from the circle for now, and it’s a wise move. I can find 13 occasions in the last 30 years where the Liberals (state or federal) have changed leaders less than 12 months before an election, and only three of them went on to win.

The last one to do so was John Olsen in South Australia in 1996-97, and that’s not a good precedent – he just squeaked in, throwing away most of a huge majority. Since then the tactic has been tried in Victoria, Tasmania, South Australia, and twice in New South Wales, each time without success. The Victorian Liberals are also lining up for a second try. Some people never learn.