Yesterday, as part of our ongoing campaign to restore balance and accountability to the Senate, GetUp released a Galaxy poll showing the Coalition ahead of Labor (35% to 33%) for the first time this year in the Senate primary vote. This represents a 6 point downward shift for Labor and a 3 point upward shift for the Coalition from our last poll six weeks ago.

The Galaxy poll was taken over the weekend, before the debate – on the same nights as the last Newspoll, which had a strong Labor showing in the House of Representatives. There was no Newspoll concurrent with the the last Galaxy Senate poll, from 7-9 September, but the two adjacent Newspolls, on the weekend before and the weekend after had Labor on 59 and 56, respectively – very similar to their lower house vote now. So why the shift in the Senate vote but not in the House?

Part of the answer, naturally, is that some Labor voters in the House of Representatives “defect” to minor parties such as the Greens and Democrats in the Senate – and with the Greens on 11% and Family First and the Democrats on 2%, likely preference flows suggest the equivalent of a two-party preferred lead for Labor of 46% to the Libs’ 35%. Finally, assuming the current undecided voters and the microparties’ preferences flow equally to both sides, that puts progressives around 56% and conservatives on 44%.

So in the end, this Senate result is not so different from recent poll results for the House of Representatives, but it leaves one important question unanswered – why the significant downward trend for Labor? One possible conclusion is that the poll is a statistical fluke. Flukes inevitably happen in a statistical science such as polling, but with a 1000 sample size and a movement of 6% – almost double the 3.1% margin of error – the movement is almost surely genuine.

A second possibility is that voters are becoming increasingly confident that Labor will win the House of Representatives – and are voting to provide a check against their power. However, most voters do not grasp the current unusual historical circumstances, in which the Coalition has a majority in the Senate and it is practically impossible for Labor to win a majority in its own right.

It would be ironic to deliver a resounding win to a Rudd government, but leave them hamstrung by a Coalition-controlled Senate – and it is unlikely that the average voter has any inkling that that would be the result of their decision to vote for Labor in the House but conservatively in the Senate.

The terrible track record of the Coalition-controlled Senate, which in 2006-2007 literally rubber-stamped 100% of its own amendments while rejecting 98% of other parties’ suggestions, has undermined our democracy’s checks and balances. And GetUp’s role in this Senate election is to make sure that voters know about it when they go to the polls.