Today’s ACNielsen makes it four in a row. Over the last fortnight each of the big polling outfits has published a set of results which has shown a jump in Labor’s already huge lead compared with the pollster’s previous result. Such unanimity among pollsters is actually quite rare.

Nielsen is the only one whose two party preferred numbers are extracted from respondents. The others estimate it from primary support. That’s what I do with the poll-mix, the latest of which is below.

Read more about methodology here.

The last time we had a change of federal government was in 1996, when John Howard defeated Paul Keating. On election-night, few people were surprised at the result, because for the previous twelve months the Coalition had invariably been comfortably ahead in the published polls – but not by anything like Labor’s leads this year.

At this stage the most likely scenario on election-day is looking very bloody, but once the campaign is called, the dynamic changes. Just as we’ve never seen such sustained opinion poll leads by an opposition as Labor enjoys today, the government will be hoping the magnitude of Howard’s recovery is similarly unprecedented.