Interesting report by Imre Salusinszky in today’s Australian on Liberal concerns about Malcolm Turnbull’s hold on his seat of Wentworth, one of those altered in this year’s redistribution.

It says that the changes “cut Mr Turnbull’s margin from 5.5 per cent to 2.5 per cent”. That’s the parliamentary library’s estimate, although it was made before the redistribution was finalised; revisions made in the light of objections are believed to have improved Turnbull’s position slightly.

Adjusting margins for redistribution change is not an exact science, but the general rule is that changes have less of an effect than they appear to.

There are numerous cases of sitting members holding on despite apparently very unfavourable change, because moving from a safe seat to a marginal changes people’s voting behaviour. Most of the time it’s voters that decide elections, not boundary commissioners.

Nonetheless, Turnbull is entitled to be concerned. Having spent so much money and effort to get into parliament, the prospect of losing after only one term would be alarming indeed. It would also be exceptionally bad news for the federal Liberal Party, whose upper ranks are starting to look very thin on talent.

So the party would be only doing its job if, as Salusinszky says, it “has been polling voters on their views of Mr Turnbull”, and on his recognition against prospective Labor opponent George Newhouse, the mayor of Waverley.

But reports of internal polling always need to be treated with great scepticism. Usually the polls that the media find out about are the ones that somebody has an interest in leaking.

It wouldn’t be surprising if the NSW Liberal Party is polling in a whole range of seats – that’s what political parties do. But Wentworth is the one we get told about, suggesting that someone in the Byzantine world of the NSW Liberal Party is running an agenda of their own.

The story is also an example of the more general danger of commentators becoming reporters. Salusinszky is billed as “NSW political reporter”, but it’s hard for a reader to forget his past as a highly opinionated commentator.

It’s a bit like having Philip Adams reading the news – you’d never be sure how much of it to take seriously.