Why coalition is relaxed about first polls

Despite the headlines of neck-and-neck opinion polls, coalition hardheads will be reasonably relaxed about the government's standing with voters on day one of the election campaign.

That's because they're relying on a trend that goes back 12 years and covers four election campaigns - early polls underestimate coalition support.

Four polls have the coalition and Labor tied at 50 per cent, after preferences. Newspoll has Labor ahead 51-49 per cent while Essential Media's rolling fortnightly poll gives Labor a four-point lead.

But as an indicator of what might happen on July 2 when voters put pencil to ballot paper, the first-flush polls are historically unreliable.

In 2010 - at the start of an election campaign that ended with an almost tied vote and a hung parliament - the coalition trailed Labor by 10 points when Julia Gillard went for broke as Australia's first female prime minister.

Three years later a dysfunctional Labor government was on the nose with voters despite the return of Kevin Rudd.

The first polls had Tony Abbott's coalition leading 52-48 per cent. On election day, the result was 53.5-46.5 per cent.

Even in the Ruddslide of 2007, the first polls underestimated support for the coalition.

Labor held a massive 56-44 per cent lead in the opening week. By election day, John Howard's coalition had halved that lead.

Howard had a better result in 2004 when the coalition turned around the first week polls - showing Mark Latham's Labor leading by four points - to retain power with a five-point-plus win.

Only one poll in this election - Reachtel - has told us how many voters are undecided eight weeks out from polling day.

Its budget-week poll, conducted before Malcolm Turnbull fired the starting gun on Sunday, showed eight per cent didn't want to say or didn't know who they would support.

History shows those voters split more heavily to the coalition than Labor on election day.