Premier Mark McGowan’s thumping victory at last weekend’s WA election was well deserved, but it also risks becoming a terrible result for democracy.

A massive 60 percent of the primary vote translated into Labor winning almost 90 per cent of the lower house seats, all but wiping out the Liberals. If Western Australia had a proportional representation voting system, like that used in the ACT, it would have delivered the Liberals a fairer outcome, ensured a more effective opposition and made WA’s democracy stronger.

While the ACT’s Hare-Clark system is often criticised for the fact that it has resulted in 20 years without a Liberal chief minister, Western Australia’s result provides an ominous warning to those who would change Canberra’s electoral system to be careful what they wish for.

In a single-member electorate system, such as that used to elect members to the lower house of the Federal Parliament, whoever gets 50 per cent of the vote plus one, after preferences, wins 100 per cent of the one local seat. In proportional representation systems, such as in the Australian Senate, each state elects 12 senators, usually six at a time at half-Senate elections. Overall, parties that win 10 per cent of the vote tend to win around 10 per cent of the Senate seats, and those who win 40 per cent of the votes win around 40 per cent of the seats. Neither system is perfect, but proportional representation does a good job of electing representatives for smaller groups and a great job of preventing the kind of wipeouts we just saw in WA.

Premier McGowan and the Labor Party are entitled to enjoy their victory. But when the dust has settled, and the 50 or more Labor parliamentarians can count the number of Liberal parliamentarians on one hand, it will be time to ask if it is a fair election outcome.

If Western Australia had a proportional representation system like the ACT’s, minority voices and minority voters like the Liberals would be guaranteed a place in its Parliament while still ensuring a majority party like Labor would hold a majority of the seats. While the single-member electorate system in WA will likely deliver the Liberals just two seats out of the 59 in the lower house, proportional representation would likely have delivered them 13.

The ACT’s five electorates each elect five parliamentarians, guaranteeing a place for the Canberra Liberals even in the face of a decisive Labor victory. At the last territory election, the Canberra Liberals won 36 per cent of the seats off a primary vote of 34 per cent. That is a pretty fair system.

If, however, the ACT had 25 small, single-member electorates under a system similar to WA, then the Canberra Liberals would have likely fared much worse. Just as the 31 per cent of Canberra voters who voted for the Liberals at the last federal election succeeded in electing zero Liberals to the federal lower house, it is likely that local Liberals would win a very small number of single-member electorates.

Instead, proportional representation has guaranteed that the ACT always has a strong, reasonably numerous opposition, along with Green and independent MPs to keep the government of the day on its toes.

There are two big winners in the WA state election: Labor and the Nationals. While the Nationals (who are not in a formal coalition with the Liberals in WA) are set to lose some seats, it is likely that their 4 per cent of the primary vote will deliver them around 7 per cent of the lower house seats. And because the Liberals look set to convert their 22 per cent of the vote into only 3 per cent of the seats, it will be the Nationals that could be declared the official opposition party.

With an electoral system where parliamentarians are elected on the basis of geography, parties with localised but deep support, like the Nationals, do significantly better than parties with widespread but shallow support, like the Greens. At the federal level, the Nationals (excluding the LNP in Queensland) won 10 seats with 5 per cent of the vote, while the Greens won one seat with 10 per cent of the vote. We are so used to this system that it seems natural to us – that the Deputy Prime Minister belongs to a party with fewer voters than the Greens, or that a government can lose the two-party-preferred vote and still win a majority of seats (as happened in 1998 with John Howard).

Democracy is stronger when the minority – like the Liberals in WA and Canberra, or the Greens – is represented properly. Holding the majority to account and reflecting alternative views makes the whole system stronger. Oppositions force ministers and senior public servants to explain themselves and speak to the flaws in government legislation, even if its passage is a fait accompli, and offer the public an alternative government they can vote for at the next election. That is hard to do when you do not have enough members to field a netball team.

A fearsome advocate for proportional representation in the Senate (but not the House of Representatives) is the Liberal Senate President, Scott Ryan. Senator Ryan has spoken at length on the contribution the Senate makes to our democracy, most recently at a webinar hosted by the Australia Institute last week. Senator Ryan was launching a report from the Australia Institute, which finds that Australians’ knowledge of the Senate is limited despite the Senate performing vital accountability and democratic functions.

Senator Ryan emphasised that proportional representation has guaranteed elections are not “winner-takes-all”. Governments can win an election but still need to negotiate to get their agenda through. He noted that this helps moderate against the kinds of wild swings in policy that have happened in countries without a democratically elected upper house. He also identified the Senate’s representation of Australian diversity, including its current 50-50 male-female split, and milestones like the election of Neville Bonner, the first Indigenous parliamentarian.

Premier McGowan and the Labor Party are entitled to enjoy their victory. But when the dust has settled, and the 50 or more Labor parliamentarians can count the number of Liberal parliamentarians on one hand, it will be time to ask if it is a fair election outcome.

The ACT’s electoral system proves there is another way. A path that produces stable and long-lasting government, but creates a space for minority voices on the crossbench. It also guarantees the opposition survives to play its vital democratic function. As with the territory’s 100 per cent renewable energy, its big investment in public transport, and recent reforms to the land tax system, once again it seems that the ACT leads the way for other jurisdictions to follow.