The decades since the introduction of STV in the Australian Senate has led to a profusion of minor parties, and the reason why this experiment has not been repeated in any of the state parliaments is obvious.
Yes, I know the Tasmanian lower house has had Hare-Clark since 1907 and New South Wales gave it a trial run in their own lower house in the 1920s, you don't need to @ me.
For the first few decades, it seemed obvious that the balance of power would only ever be held by Independents and the DLP, a Catholic and Anti-Communist splinter from the Labor Party. These Senators generally used their powers responsibly, never going so far as to deny supply to a Government with the confidence of the House of Representatives. However, the 1970s saw the DLP erode - for starters, their raison d'etre of keeping the ALP out of government was made obsolete by the majority won by Gough Whitlam, and then the Gair Affair proved an embarrassment to a struggling party. In the double-dissolution election of 1974, only Queensland's Condon Byrne held onto a seat, although he was joined by Brian Harradine from Tasmania the next year. But this was the point at which the DLP ceased to be a national force, losing both seats in their former stronghold of Victoria and falling back in the other large state, New South Wales.
There was a brief resurgence in 1977, thanks to a deal with the Country Party finally paying off. The Country and Democratic Labor parties in Western Australia had entered into a 'National Alliance' for the 1974 and 1975 elections, both of which returned a single Country Senator, and in 1977 William Sullivan of the DLP was begrudgingly given the top spot on the list, and served until the double dissolution of 1983.
However, by this time, there was another third party on the scene. Don Chipp had formed a new centre-line, small-l liberal party out of the wreckage of Steele Hall's party in 1977, and quickly attracted protest votes (largely from social-liberals and environmentalists) in Victoria and South Australia. The Australian Democrats were much more forthright than the DLP, and brought down the Fraser Government over the GST issue in 1983, precipitating a double-dissolution in which they took seats in New South Wales and Western Australia. For a moment, the ADs were the dominant third party - but another election in 1984, in which the Nuclear Disarmament Party took 8% of the vote from almost a standing start, cost them the gains from their brief ascendancy.
The NDP, led by the rock musician Peter Garrett, married peace activism with environmentalism, and elected two Senators in 1984 - Garrett himself in NSW and Jo Vallentine in Western Australia. This pair took the third-party vote from under the Democrats' noses in those states, but fared less well elsewhere. Now, the NDP and the Democrats have a lot of ideological common ground, but all attempts to unite the parties have foundered on several issues - such as the NDP's feeling that the Democrats aren't sufficiently strong on 'green' issues and the ADs' feeling that the NDP are a bunch of flakes. Their Senators have made a habit of being expelled from the Senate after finding that they're ineligible on citizenship grounds, the most recent example being Scott Ludlam. Another issue is the contention that the NDP are riddled with entryists from the Socialist Workers' Party and other Communist sects, with Lee Rhiannon's leftist heritage being a common cry from centrist Democrat spokespeople such as Fiona Patten and Nick Xenophon.
Another proposed solution to AD/NDP relations has been electoral reform to allow 'Group Voting Tickets' which would make it easier for parties to transfer votes between one another without the voters getting a word in edgeways, but this has never passed a second reading because it would obviously lead to even greater electoral fragmentation.
The DLP, by contrast, have not been in demand for mergers with the other minor parties. However, they have benefited in Queensland from a deal with the Nationals along similar lines to the short-lived deal in WA. The Queensland Nats didn't share Senate lists with the Liberals, and instead arranged to have DLP candidates heading their list at every second half-Senate election. This is how Condon Byrne and Geoffrey Maule managed to stay in the Senate and keep Brian Harradine (very popular in Tasmania thanks to his firm stance on the Franklin Dam) company in the lean years. However, tensions grew from the mid-90s on, when Senator Pauline Hanson became genuinely popular in the state and the DLP started winning seats in the Queensland Parliament. The feeling was that the party could win a second Queensland Senate seat if they left the comfortable arrangement with the Nationals - this feeling proved to be accurate in 2010, by which time the Nationals (jumping from one extreme to another) had entered into a full merger with the Liberals.
Hanson's leadership was a golden age for the DLP, but caused a certain amount of internal friction. Hanson's leadership style was autocratic - too much so for Steve Martin, the Tasmanian Senator, who resigned in outrage at some slight or other and was succeeded by Jacqui Lambie - and her focus was too much on anti-Asian rhetoric which didn't easily mesh with the focus on reproduction that most of the Catholic DLP voters wanted to hear. The biggest success of the Hanson period, ironically, was her seduction of Bob Katter as the Party's first member of the House of Representatives since the 1950s - and as a more suitable leader.
Under Katter, the DLP has become a consistent winner of the final seats in Queensland and Tasmania, but fortune has eluded them in the other states, where the Democrats and the Nuclear Disarmament Party have dug themselves in. In the last couple of decades, the Senate has become home to frequent attention-seeking minor-party stunts and (more seriously) threats to block supply, with only the Democrats really aspiring to make the committee system work to scrutinise the lower house - although how much of this attitude is centrist sanctimony is up for debate. In the recent debate on introducing PR to the South Australian upper house, spear-headed by Nick Xenophon, the overwhelming response was "The Council's a joke, but why would we want to fix it by making it like the
Senate?"