NSW votes next Saturday. All the polls point to the same outcome: a decade-old NSW Labor government for the coalition to kick around at the next federal election. No matter what goes wrong, they'll always have that.

The state with a third of the House of Representatives seats has a history of punishing the federal counterpart of its local administration. Start with July 1987, when Bob Hawke successfully sought a third term against the then opposition leader John Howard. There was a 1 per cent national swing to the coalition, but the NSW component, 2 per cent, accounted for nearly all of it.

But three years later there's a change of heart. While other states swing in aggregate by 2 per cent to Andrew Peacock, NSW goes back to Hawke - also by 2 points.

What happened to the folk of NSW between 1987 and 1990? They demolished the 12 year-old Wran/Unsworth government. Liberal premier Nick Greiner brought many things to NSW, but votes for federal colleagues wasn't among them.

The pattern continues to this day. In March 1993, under the then Liberal premier John Fahey, NSW swung to the Keating government by more than twice the rest - 2.5 versus 1 per cent. Bob Carr is in charge by March 1996, and so the state's contribution to the Howard landslide is massive - 7 per cent compared with 4 per cent elsewhere.

In 1998 the swings to Kim Beazley were 4 in NSW and 5 per cent outside the state; and in 2001, it shifted back to the coalition, 4 and 1 per cent respectively. So the magnitudes have varied but not the rule: swing-wise, NSW outperforms the rest of the country for the federal coalition when Labor is in power there, and underperforms when it's not.

November 2001 was the high point of the federal coalition's NSW component - 28 seats out of 50. But 10 years ago last Thursday, Paul Keating's "sweetest victory of all" left it with only 17, its direst outcome in memory, and one that would have given Beazley a comfortable win if repeated 16 months ago. You've heard the usual reasons for this turnaround: "Sydney is different." They generally mention "aspirational voters", high incomes, real-estate prices and migrants, but none of them work because the biggest swings to John Howard in 2001 weren't in Sydney, but on the NSW south coast. Gilmore, Throsby and Cunningham swung by 10.6, 7.3 and 6.6 per cent respectively. It's a state - not a Sydney - thing. That thing is Bob Carr. He's the federal government's dream Labor Premier: not charismatically endowed, roundly considered just OK, but he stays in power. A John Brogden win next weekend would be wonderful news for Simon Crean.

Peter Brent is editor of mumble.com.au, a website that looks at electoral behaviour.