I can speak firsthand here and say that the answer is yes. Australia uses Instant Runoff Voting for our House of Representatives, and Single Transferable Vote for our Senate. I’ll concentrate on the Reps here because it’s by far the more politically powerful of the two, though it’s worth noting that STV being a somewhat-proportional system makes it even better for minor parties.

The Australian political climate was, for most of my youth, not too different from America’s. Our conservative “liberal national coaltion” is not quite as awful as the Republicans, and Labor is a bit left of the Democrats, but it was very much a two-party system in practice. In 2010, after years of slowly doing better and better, the Greens won their first seat. They came second on first preferences, at 36.17% to Labor’s 38.09%. But the Greens received preferences from minor parties like the Sex Party, and even from the LNP in their attempt to destabilise Labor, and ended up winning the seat 56.04–43.96

Now, this is the innermost city electorate of Australia’s most progressive city, and you’ll note that even in FPTP, Labor would have won, which wouldn’t be a disastrous outcome. But the Greens saw an over 13 point swing toward them in that election alone, which is only possible in a situation where voters aren’t afraid of the spoiler effect leading to the LNP winning.

They’ve kept that seat ever since, and at the last election in 2022, the Greens almost won that seat entirely on first preferences, with 49.6% of the vote, and 60.2% after preferences were distributed.

Even more excitingly, in 2022 the Greens won their second ever seat. And their third and fourth. These all in a much less typically progressive area, the inner Brisbane seats of Brisbane, Griffith, and Ryan. Brisbane and Ryan previously belonged to the LNP, and Griffith was previously Labor. In Brisbane and Ryan, the LNP lead on first preferences, but the Greens lead in Griffith. If it were only down to these three parties, Labor would have won Brisbane, since the Greens came third by just 11 votes. The Greens would have won Ryan and Griffith. But thanks to preferences coming in from the smaller candidates (most smaller candidates are further right than the LNP, but most notably the Animal Justice Party pulled in a couple of per cent), the Greens finished ahead of Labor, leading to Labor being eliminated and most of their votes going to the Greens candidate. As a result, right now, I am living in an area represented federally by a Greens member. I also have a Greens state representative, and I’m hoping that something similar will play out so that in just under 2 months, I’ll also have a Greens councillor.

The rise of the Greens party in Australia has been incredible over the last couple of decades. It’s still slow progress and there’s a long way to go. Sadly IRV is not a proportional system, so despite polling about 10% nationally they still only have 2.7% of seats—if you’re going to switch systems, try to switch to a proportional one if you can!—but it is a system that allows for this kind of growth to play out in a way that it simply can’t when voters are forced to vote strategically for the least-worst of two main options, lest you get 2000’s Ralph Nader play out in Florida.