Is Malcolm Turnbull disposable as Liberal leader and thus Prime Minister? This week's Fairfax Ipsos opinion poll contained terrible news for him. His government was 10 percentage points behind the opposition in two-party-preferred terms (55 per cent to 45 per cent). He came to the position on the grounds of his popularity but, for various reasons, has failed to live up to expectations in this regard. The polls continue to destabilise his position.

There is a recently published book that should be selling like hot cakes in Parliament House's bookshop. Not every Liberal MP will read it because they don't think they have anything to learn from an academic analysis. But they should.

The book, written by University of Sydney emeritus professor Rodney Tiffen, is Disposable Leaders: Media and Leadership Coups from Menzies to Abbott. He has assembled a database of the 73 federal and state political party leaders in Australia who have been disposed of by their parties since 1970.

The emotive term for such an event is coup, though, in unemotional terms, it is best described as a legitimate event in which the sitting leader – even if prime minister, such as Kevin Rudd, Julia Gillard and Tony Abbott – is challenged and beaten in a democratic leadership contest.