The starter’s gun has fired. Abbott and Rudd are off. But there is another race.

That race is more like the City to Surf, with literally hundreds of runners – the race for the Senate. No legislation gets through without Senate approval. Nearly all the legislation Labor got through in the last term – and there was a lot of it (too much) – was passed with the support of the Greens.

On the day the 7 September election was called, two ill-informed, even mistaken, statements were made on TV by two senior press gallery journalists. One was that the Greens would do badly now that Labor is doing better under Rudd. More of that anon. The other was that the Greens would do badly in the Senate because they are coming off a high base. Indeed, the Greens have nine senators – the most they have ever had. But that is not a high base because only three of them are up for re-election.

Only half the Senate will be elected on 7 September – those senators who were elected in 2007. Only three of them were Greens, one each in Tasmania, South Australia and Western Australia. The other six Greens were elected in 2010 – one in each state. So the Greens are in fact coming off a low base. The three sitting Senators could well retain their seats and perhaps a Greens be elected on one, two or three of the other states.

The other statement that Labor’s increased vote (according to recent polling) will make it harder for the Greens. Not so. Policy and the Senate counting method suggest otherwise. In 2007, Labor was running on a softer, more compassionate refugee policy and a tougher climate change response than either the then government or its current policies. A lot of otherwise Green-leaning voters were comfortable with Labor and voted for them. Not so now. Labor’s increased vote since Rudd came to power has come from the Coalition, not the Greens. This will in fact help the Greens in the Senate, not hinder them. This is because of the voting system. To get one of the six Senate seats in a state you need one-seventh of the vote plus one. If six candidates do that there is no room for anyone else to be elected. So you need 14.3 per cent of the vote after preferences. The major parties always get at least two seats each with an easy 28.6 per cent of the vote.

To get a third seat they need 43.9 per cent. That is a harder ask, even after preferences. (To get a fourth seat they need 57.2 per cent after preferences. It has only ever been done once and won’t be repeated.) Now, preferences come from two sources in the Senate: first, from shrapnel, minor and independent candidates getting eliminated and, second, from the over-quota from major parties which do not get a third seat. So if either of the major parties is shy of the 43.9 per cent, the preferences of all the vote above the 28.6 needed to elect the first two of its candidates must be distributed.

In Labor’s case, if a lot of that vote has been grabbed by Rudd from the Coalition it will mean what had hitherto been Coalition vote will, in effect, go to the Greens. Reinforcing this effect is the tight running of preferences in the Senate. There are so many candidates in this City to Surf race that very few voters can be bothered filling out preferences of their own choice by numbering all the squares from 1 to, say, 50 to 100 candidates. Instead, they vote above the line. Under the system they just put a 1 besides the party of their choice and the preferences are deemed to be allocated according to how the party allocated them with the Australian Electoral Commission. More than 90 per cent of voters do this.

It is a delicious irony in a way. The major parties in the 1980s thought they had rigged the system to favour themselves. They increased the size of the Senate so that six senators were elected from each state every election, instead of five. With five senators they needed 49.8 per cent of the vote to get a third senator. With six senators they needed just 43.9 – more senators for less vote. They imagined the minor parties would be shut out.Also, the above-the-line voting was supposed to give the major parties more power.

What happened in fact? The primary vote of the major parties has fallen sharply since the 1980s. Minor parties and independents have not been shut out. Indeed, since the changes we have had an ever-increasing array of minor-party and independent senators. Do not expect this election to be any different. Does that mean the Greens with between nine and 12 senators will have the balance of power in the Senate? Well, yes, if you look at it in the traditional tunnel-vision way. But there is another way of looking at it. If the Coalition wins in the House of Representatives, you can expect the Greens to oppose everything they do. In that case, Labor will have the balance of power. Legislation Labor agrees to will go through; legislation it opposes will be blocked.

If Labor wins the House of Representatives (which looks increasingly likely), the Greens will be its virtual coalition partner on most things. Anything tough and controversial on things like cuts to public spending; refugees or the environment will depend on Coalition support in the Senate. In that case the Coalition will have the balance of power.

In any event, an enormous amount will depend on the outcome in the Senate. A Coalition majority in the Senate now seems extremely unlikely.

crispin.hull@rubyreef.com.au