The Coalition might not be able to count on a Senate majority after a likely Labor win at the election.

The ACT’s Liberal senator Gary Humphries is in deep trouble, and current indications point to a possible defeat by popular Greens candidate, Kerrie Tucker.

I had always been sceptical of the proposition that the Liberals could lose their ACT Senate seat, but after looking at the latest Morgan polling – which puts Liberal support at just 24 per cent and the Greens at 17 per cent – it now looms as a distinct possibility if those trends prevail.

Unlike new Senators from the states, who don’t take their seats until after July 1 next year, the four Senate seats in the ACT and Northern Territory are decided at the same time as the House of Representatives election, and the successful candidates take their places immediately.

If Senator Humphries were to lose his seat to the Greens, the Coalition would immediately lose its majority.

Despite growth in public service jobs and a booming economy in Canberra, the Liberals are on the nose in a predominantly Labor town, and Humphries was always going to be in trouble if his primary vote fell below 28 per cent (The quota is 33.4). He will be all but friendless on the ballot paper with only Family First likely to preference him.

On the other hand, Labor’s Kate Lundy will have a huge surplus after her quota, the great bulk of it above the line, and it has to go somewhere – and that will not be to the Liberals.

The long-serving Liberal Margaret Reid was forced to preferences in 1998, and the Liberals have never taken the seat for granted – but languishing on just 24 per cent they can just about kiss it goodbye.

Now, in that scenario, it puts the heat on Family First’s Senator Steve Fielding, to whom the Coaliton would turn for the extra vote it needed to block ALP legislation if Labor is indeed the next government.

Does Senator Fielding support the popular mandate, or does he cosy up to the defeated Liberals? And if he does the latter, is it because he likes them or is simply angered at Labor’s preference deal with the very secular Greens?