Most people accept that the federal Liberal Party is in a bad way, but it doesn’t lack its boosters. This morning’s Age features Peter Costello celebrating the party’s victory in the Higgins by-election, while criticising the Greens for their arrogance and poor tactics, and offering them some free political advice into the bargain.

Most of what Costello says is quite sensible. It’s hard to beat this, for example, as a summation of Greens’ candidate Clive Hamilton:

The Greens chose a bad candidate. Their central command overrode local supporters to impose someone who lived in Canberra. Most people think an MP should represent locals to Canberra. The Greens had the idea they could represent Canberra back to the locals.

It’s also true (although hardly a revelation) that the Liberals were helped rather than hurt by Labor’s decision not to field a candidate. Nor does Costello shy away from drawing a moral: “To maximise their joint position, the Greens and Labor need to run three-cornered contests, just like the Liberals and Nationals in regional electorates.”

It’s been psephological orthodoxy for a long time that the coalition is hurt rather than helped by three-cornered contests. The truth is probably a lot messier — sometimes it helps, sometimes it doesn’t — but it will be interesting to see if Costello’s supporters now reverse themselves and argue for running candidates against the Nationals across the board.

It’s fine to celebrate one’s victories, but the danger for the Liberals is that they will misunderstand, and therefore systematically underestimate, the threat from the Greens. If you’re convinced, as Costello claims to be, that almost all Greens votes come from Labor, you won’t see any need to adjust your own policies to stem the flow of Liberal voters to the Greens.

It’s true that Labor can deliver most, but not all, its votes to the Greens as preferences, or as primaries if it doesn’t run. But that doesn’t tell us anything very interesting, since exactly the same is true of the Liberals. (Costello also thinks “the Greens can deliver more than 90% of their preferences to Labor”, whereas the real figure is a bit under 80%.)

More generally, Costello and his party need to guard against falling prey to the same faults they identify in others. The Greens may have a problem with over-confidence (although I wonder if this is an urban myth — the Greens I talk to always seem to err on the side of modesty in their expectations), but they would hardly be alone in that: how many of the twenty-something losing Liberal leaders of the past decade have conceded in advance that an election was a lost cause, or even admitted afterwards that the result was worse than a minor setback?

Similarly, self-righteousness and overblown rhetoric are not confined to the Greens. The warning that “moral absolutists rarely deliver what they promise” should not be lost on Tony Abbott and Kevin Andrews. And Costello’s closing line, “Sanctimony can make you feel good but it rarely appeals to the listening audience”, while undeniably true, might also be thought to have a wider application.