A number of senior union figures have said that a double dissolution election would be bad for the progressive side of politics. It may be, but it is more likely that a half-Senate election would result in the conservative side of politics controlling the Senate. A double dissolution election, however, gives the progressives a better chance.

Some unionists argue that, in the event of a double dissolution, some or all of those crossbenchers who have voted against the Turnbull-Abbott government would lose their seats — presumably to be replaced by Coalition senators. Senators Glenn Lazarus and Jacqui Lambie however, with the lower double dissolution quota, may poll well enough to hold their seats, or they could be won by a Labor or Greens candidate.

The bigger risk is that, in a half-Senate election, the votes of the continuing two or three less-conservative crossbenchers become almost irrelevant in Parliament as they would likely lose their grip on the balance of power.

Analysis of Senate numbers in a half-Senate or double dissolution election is always tempered by the fact that the result of the coming election is a prediction, but it is clear that the progressive side of politics is starting from a numerically weak base of continuing senators, if a half Senate election were held.

If the Coalition wins government at the 2016 election, controversial legislation like the Australian Building and Construction Commission bill could pass both houses of Parliament, whether a half-Senate or double dissolution election is held, and whether or not there is Senate voting reform.

Labor and the Greens both had such a poor Senate election in 2013 that, combined, they only have 14 continuing senators should a half-Senate election be held in 2016. While both parties enjoyed a good Senate election in 2010, the seats of those combined 21 senators that were won are all up for election this year.

An election victory for the Coalition is likely to deliver a reasonable half-Senate outcome for it, too. The Senate make-up in that scenario, added to the result from 2013, is highly unlikely to be a good outcome for the more progressive side of politics.

The Coalition will have 15 continuing senators plus it will retain two from the territories. The Coalition could win close to half the state Senate seats in a half-Senate election, taking it to a total of about 34 seats, five short of a majority in the 76-member Senate.

The reality is that most of the seven continuing crossbench senators could fairly be described as being from more right-wing micro-parties.

Instead of the six crossbench senators it requires now to pass legislation, the Coalition would only need support from four or five other senators. If it could secure the backing of senators like David Leyonhjelm, Bob Day, Dio Wang and Nick Xenophon — and almost certainly another from his party who will be elected in South Australia — the Coalition could be confident it would get much of its agenda through the Senate.

The votes of continuing senators Ricky Muir and Glenn Lazarus, who are less conservative, and the more unpredictable Jacqui Lambie, would probably become much less important as the Coalition would be able to rely on the more right-wing crossbenchers — with the price of this support being Coalition support for some of their more crazy policies.

Progressive voters should be worried about the Coalition’s draconian ABCC bill with its attacks on civil liberties, the rights of working people and the effective removal of enterprise bargaining agreements.

But let’s not forget how close the ABCC bill came to passing under the existing Senate. The Coalition was only one vote short in August. Lambie was for the ABCC but voted against it because the Coalition did not give in to her demand that the CFMEU be deregistered.

The Coalition is highly unlikely to win control of the Senate in its own right in a double dissolution. Articles by Antony Green, Ben Raue at The Tallyroom and Kevin Bonham make that clear. In part, this is because both major parties poll a lower vote in the Senate than they do in the House of Representatives, and neither major party has come close in the last few elections to polling the 50%-plus of the vote needed for a majority in a state in a Senate election. Also strong polling for the Nick Xenophon Team means the Coalition are likely to win fewer than half the South Australian Senate seats, which makes it tougher for them to get an outright Senate majority.

In fact, a double dissolution election provides an opportunity for Labor and the Greens to erase the impact of their poor Senate result in the 2013 election, instead of it being a burden in the Senate until the 2019 election. With the quota in a double dissolution election being 7.7% for each of the 12 seats in a state, if Labor can win four or five of those and the Greens one or two — so that, combined, they win six seats in each state and therefore half the Senate seats — together they would be able to block legislation.

A combined vote of 46.2%, after distribution of preferences from other parties, would be sufficient to win six of the 12 seats in each state and stymie the Coalition in the Senate. That is not an unrealistic outcome, considering Labor and the Greens won more than half the Senate seats in the 2010 election — and winning a seventh seat for the progressive side in some other state is a tall order, but not impossible.

Senate voting reform and a subsequent double dissolution election will probably help the Labor Party. Labor has lost Senate seats to micro-parties in the current Parliament because of group voting tickets: Senator John Madigan defeated the third Labor candidate for the sixth seat in Victoria in 2010 (the third Coalition candidate was trailing Labor in the count), and in South Australia in 2013 the second Labor candidate should have won a seat instead of Family First.

Some who oppose Senate voting reform complain that the new Senate election system will not allow Labor to gain a majority in the Senate. Labor has not held an outright majority in the Senate since 1951. It has relied on the Democrats, Greens, independents and a number of small parties to pass legislation when in government, and to defeat Coalition government bills when in opposition. That will continue.

To blame what would be a fairer Senate voting system for implementation of the Coalition’s agenda — should they get the vote necessary to win a majority — is flawed logic. Many in Labor know that, but it seems that some Labor MPs will not let it get in the way of vilifying the Greens and retaining an undemocratic election system with the ability to do back-room preference deals associated with group voting tickets.

It is true that some or maybe most of the crossbenchers will not be re-elected in a double dissolution, but it is simplistic and probably wrong to think that following a half-Senate election result the better crossbenchers could prevent the Coalition implementing its agenda. Analysis shows that half the existing crossbench votes with the Coalition half the time, or more, anyway.

The silver lining to this gloomy story is that the Coalition is losing public support, which means there is a chance of defeating it in the election. There is also a chance under a new fairer Senate system with a double dissolution election that the Greens and Labor could control the Senate, even if it is just being able to block legislation. There is a lower chance of achieving that if a half-Senate election is held. The balance of power would be held by either the Nick Xenophon Team alone, or maybe with a couple of right-wing crossbenchers as well. That suits the Coalition.

Surely it’s time Labor and the Australian Council of Trade Unions recognised that the Greens are not the enemy. If we unite, we can defeat the real enemy: the Turnbull government.