On Wednesday Alex Turnbull, who has been campaigning for voters to evict the Liberal Party from his father's former seat of Wentworth, switched his support from Labor to independent Kerryn Phelps on strategic grounds. Amusingly, Turnbull jnr justified his support by reference to a popular American text called "Gaming the Vote" by William Poundstone, and posted a colourful excerpt explaining how the squeezing out of a centrist candidate who finishes in third places can lead to "unpalatable, Wizard-or-Lizard dilemmas". After Clinton-vs-Trump, or even the utter farce that has been the present term of Australian parliament, wizards and lizards are both sounding pretty good at the moment.
The idea here is very simple: if Kerryn Phelps makes the final two she is more likely to beat Dave Sharma (Lib) on preferences from Labor (which will include some votes originally for the Greens and minor candidates), than Tim Murray (Labor) is to beat Sharma on Phelps' preferences should he make the final two. Phelps is (mostly) seen as the more centrist candidate in an electorate that has never elected a Labor MP. There will be voters who want to send a protest vote against the Liberals for disposing of that other Turnbull or whatever other reason, but who cannot bring themselves to vote Labor.