In a double dissolution each major party was in the hunt for five seats out of 12, needing about 38 per cent of the vote.



In a half-Senate election a major party cannot get half of five seats (two and half seats out of six). It either gets three, needing three times 14.3 or 43 per cent of the vote after preferences, or two, needing two times 14.3 or 28 per cent of the vote.



The major parties are each always going to get more than 28 per cent of the vote and two senators, but, in the current environment, never reach 43 per cent and three senators.



So the starting position this election is two senators for each of the major parties in every state, leaving the remaining two in each state for minor parties.



A popular misconception is that all that matters is whether you put Labor before Coalition or vice versa however high up or low down they are on your voting slip. That is true in the Reps, but not the Senate.



Preferences FROM major parties are crucial. If, for example, the Coalition got, say, 38 per cent of the primary vote in NSW, 28 points of that would go to electing their first two senators and the remaining 10 points would flow down to the voters’ next preferences, in effect, at a discounted rate of 10 divided by 38, or a tad over one quarter of a value.



It is extremely unlikely that any minor party will get the necessary 14.3 percent quota with first-preference votes, so two senators in every state will be relying on preferences from the major parties and other minor parties. They will make up the crucial Senate crossbench which decides the fate of nearly all contentious legislation in Australia.



But a very large number of Australians who vote at this election will get no say in who they are. Importantly, these disenfranchised voters will include people who have put one of the major parties as their first preference.



This is because unlike in 2016 when the majors were in still in the hunt for the last couple of seats in each state, this time they will be out of the picture after two of their senators are elected in each state, and if major-party voters have limited themselves to six preferences, none of which include the two candidates vying for the last two seats, their vote exhausts. They get no say in who should be the last two senators.



But surely a Labor voter would want the HEMP party rather than a Fraser Anning Party or One Nation senator. Surely, a Coalition voter would prefer a Hinch Party senator to a Green.