Apologies for the inactivity - been a bit busy lately. Those who are interested will already be aware that Malcolm Mackerras has published his calculations of post-redistribution margins, answering (more or less) many queries raised on this site’s comments threads when the proposals were first made public. His figures offer a few surprises: Labor’s newly acquired seat of Parramatta has moved back into the Liberal column; John Howard has only lost 0.3 per cent from his margin in Bennelong; and Mackerras gives the Nationals a margin of 7.9 per cent in the new Queensland seat of Wright, whereas my own calculation (and reportedly that of the Nationals) had it at about 5.5 per cent. The following tables indicate which seats have shifted in which direction and by how much.

The New South Wales federal electoral redistribution that was unveiled yesterday is of more than usual significance, at least if one school of thought regarding the prime ministerial succession is to be believed. It had been widely surmised that the Prime Minister was awaiting its impact on his precarious electorate of Bennelong, which he carried by an uncomfortable 4.3 per cent in 2004, before deciding whether to lead the party into the next election. Some hypothetical redistribution scenarios had Bennelong either being abolished or shifting westwards into Labor territory as part of a wholesale shake-up of Sydney electorates. The more dramatic of these scenarios were predicated on the assumption that a metropolitan seat would be abolished, but former Nationals leader John Anderson’s electorate of Gwydir has instead been nominated for the chop, cancelling out the good turn done to the Nationals by the Queensland redistribution. This means that adjustments in Sydney have been relatively modest, but they have been sufficient to make life somewhat less comfortable in Bennelong. According to an early estimate by Malcolm Mackerras (cited by Imre Salusinszky in The Australian), the electorate’s absorption of the Ermington area from Labor-held Parramatta will cut Howard’s margin to about 3 per cent.

Another leading Liberal to feel the pinch is Malcolm Turnbull, whose electorate of Wentworth will now extend westwards beyond blue-ribbon beachside suburbs and into the green-and-red inner city, reducing the return on his not inconsiderable investment. Turnbull won the seat with a 5.6 per cent margin in 2004, although the result was distorted by Peter King’s attempt to hold his seat as an independent (King won by 7.9 per cent in 2001). The addition of Woollomooloo and Kings Cross is reckoned by those in the know to have cut his margin to about the same level as Howard’s. It has been a much better redistribution for another Sydney Liberal newcomer, Greenway MP Louise Markus, who trades Labor-leaning outer urban areas for the Shire of Hawkesbury, formerly part of Macquarie. After winning the seat at Labor’s expense in 2004, Markus should now be fairly safe. Jackie Kelly has not done well out of the adjustments to her seat of Lindsay, where a move east into St Marys (formerly in safe Labor Chifley) will bite into her 5.3 per cent margin.

On Labor’s side of the ledger, Parramatta has been substantially redrawn so that the Parramatta town centre is now in neighbouring Reid. Opinion seems divided on who this will benefit, so it seems safe to conclude that Julie Owens’ 0.7 per cent margin will be little changed. Labor should get a boost in its other precarious Sydney seat, the southern suburbs electorate of Banks, which expands northwards to take Bankstown from Blaxland. Their other loseable seat, the inner west electorate of Lowe (3.3 per cent), has undergone a number of adjustments that should largely cancel each other out. Member John Murphy will suffer slightly from the loss of more than 10,000 voters in the Ashfield area to Grayndler to the south-east, and perhaps make a net gain from extensions to the south that add Liberal-voting Strathfield South and Labor-voting Croydon Park.

All of Sydney’s electorates have been altered to some degree, but the decision to abolish Gwydir means that the biggest changes are in country seats that are off Labor’s radar. Most of Gwydir’s geographical area has been absorbed by the already substantial seat of Parkes, which now accounts for about half the state’s territory and has only Dubbo for a large population centre. The most significant knock-on effects are on Calare, which moves inland beyond the Bathurst base of independent member Peter Andren (UPDATE: Andren’s electorate office is in Bathurst, but as Mountainman notes in comments, he is more closely associated with Orange which will remain in the electorate), and Macquarie, which fills Calare’s void by moving west beyond Sydney’s outskirts. Poll Bludger comments regular Geoff Robinson notes on his blog The South Coast that this roughly returns these electorates to the areas they covered before 1977, when Calare was a safe seat for the Nationals and Macquarie mostly held by Labor. Macquarie has since been won by Labor only in 1980, 1983 and 1993 (the current member, Kerry Bartlett, won by 8.9 per cent in 2004), while Calare was held by Labor from 1983 until Andren’s debut in 1996. Robinson notes that Andren must now decide “whether to go for Macquarie and hold it against Labor or to fight the Nationals in the new Calare”. It should not be inferred that Macquarie is out of bounds for the Coalition, but Labor won the corresponding state seat of Bathurst by 6 per cent more than the state average at the 2003 election, and the consensus view is that it’s a Labor-leaning marginal.

The redistribution has inevitably brought changes to the state’s rapidly growing and electorally sensitive north coast, though none are headline-grabbers. The northernmost coastal seat, Richmond, was one of three Labor gains at the 2004 election, when Nationals member Larry Anthony was voted out by the narrowest of margins. The redistribution has reunited the electorate with the northern part of the Shire of Lismore, which it last contained before the 1993 election. At the centre of this area is Nimbin, and it is accordingly noted for its strong counter-cultural element. This area has been added in exchange for Wollongbar and Alstonville in the electorate’s south, which split nearly 60-40 in the Nationals’ favour in 2004. While these areas only account for about 7000 voters each out of a total of 94,333, Labor member Justine Elliot will presumably enjoy a slight boost to her margin. However, this is a case of swings and roundabouts for Labor, since both areas have been exchanged with its very marginal neighbour Page, held for the Nationals by Ian Causley on a margin of 4.2 per cent. Page also gains about 5500 voters around Yamba from its southern neighbour Cowper, which is unlikely to make much difference. Cowper itself is potentially winnable for Labor, currently being held for the Nationals by Luke Hartsuyker with a margin of 6.4 per cent, which will not be much changed by its exchange of Yamba in the north for Kempsey in the south. The Hunter region seat of Paterson, where the Liberal margin inflated from 1.5 per cent to 7.0 per cent in 2004, exchanges a Labor area north of Newcastle for an even more Labor area further along the Hunter Valley, which should cut the margin slightly.

In a potentially bad omen for Labor, the famously marginal seat of Eden-Monaro has extended westwards into Farrer in exchange for the loss of its anomalous territory to the north of the Australian Capital Territory, a knock-on effect of Farrer’s gain of Broken Hill at the expense of Parkes. With the addition of the Shires of Tumut and Tumbarumba, Liberal member Gary Nairn should enjoy some extra padding on his current margin of 2.2 per cent.

UPDATE: Malcolm Mackerras has posted his calculations of post-redistribution margins at Crikey.