In August 1983, some Liberal MLAs decided they'd had enough of Bjelke-Petersen's shit and voted against the Government on an accountability motion. They were fired from Cabinet for this, and decided to pre-emptively coup the Liberal leadership rather than get expelled from the party. Bjelke-Petersen proclaimed the Coalition dead, and to prevent the now-independent Liberals being able to force a snap election, he prorogued Parliament for the nine weeks remaining until the October 1983 general election. It had been in session for fifteen days.
The result of the Liberals trying to go it alone was an utter bloodbath, as the National campaign machine set about ratfucking all sitting Liberal MLAs and the ones who had toppled the Coalition in particular. As it turned out, Brisbane was quite willing to vote for National candidates if the Liberals had proven themselves willing to work with Labor, and when it was all said and done, only eight Liberals were left standing. Bjelke-Petersen was still one seat short of a majority, so he invited Liberal MLAs to cross the floor and join the National party room. Two did, and the result was the first National majority government in Australian history.
Given essentially unlimited power (Queensland, unlike every other Australian state, has a unicameral legislature), Bjelke-Petersen set about once again reshaping Queensland in his own image. He started by giving himself a knighthood "for services to parliamentary democracy" - ironically, his next big act would be to pervert the course of parliamentary democracy by making electoral malapportionment even worse than it had been. The Assembly was expanded from 82 to 89 seats, most of which went to serve population growth in the deeply conservative Gold and Sunshine Coasts, and a new western zone was introduced with an even lower electoral quota than the country zone.
By 1986, as the federal Liberal Party continued to fight among themselves in opposition, Bjelke-Petersen and his hard-right real estate developer friends (the "white shoe brigade", as they were called) got it into their heads that he, the Premier of fifteen years standing who crushed all enemies in his path, be they teenagers protesting apartheid or beleaguered Liberal backbenchers, would make a far better Prime Minister than any of his Liberal counterparts. The "Joh for PM" campaign, soon renamed "Joh for Canberra" as its boosters began to realise that Bjelke-Petersen's approval rating outside Queensland was close to zero, rested on a flat income tax with indirect taxation to replace lost revenue, tougher measures against unions, protesters and Aboriginals, and restricting the power of the federal government.
"Joh for PM" would turn out a spectacular failure, likened by observers to Napoleon's invasion of Russia, but just as Napoleon remained popular in France, Bjelke-Petersen still had great clout in Queensland. Although Labor won the popular vote in 1986, as they had in 1983, the new electoral map allowed the Nationals to expand their majority to a comfortable nine-seat margin.
The wheels began to come off the National train in May 1987, when the
Courier-Mail (Brisbane's newspaper of record) and the ABC unveiled a sprawling web of prostitution and illegal gambling in and around Brisbane, enabled by a corrupt state police. This wasn't anything new by itself, journalists tended to expose similar webs of corruption every now and then only to get sued for libel by the infamously litigious Bjelke-Petersen. This time though, Bjelke-Petersen was out of state campaigning to be made Prime Minister-candidate, and his more principled deputy leader ordered a full independent inquiry in a Cabinet meeting the day after the ABC's tell-all documentary aired.
The resulting Fitzgerald Inquiry saw three Cabinet ministers jailed, the state police commissioner jailed and stripped of his knighthood, and an irreparable rift in the National Party between those who wanted the inquiry carried to term and those who believed it was a politically-motivated attack on the Government. Three guesses which side Bjelke-Petersen fell on.
After a long and confusing struggle against his erstwhile deputies, Bjelke-Petersen finally threw in the towel in November 1987. He'd tried to stay on as Premier even after the National party room voted him out as leader, but this was clearly insane, and the Governor eventually forced him to retire from politics altogether. In the ensuing by-election, he backed the LaRouchite candidate against his nominated successor (future federal National leader Warren Truss), and the former won in a major upset. Bjelke-Petersen would spend most of 1988 giving evidence to the inquiry, for which he was later tried for perjury and acquitted by a hung jury (later found to have been led by a Young National).
The new Premier, former Health Minister Mike Ahern, tried to be a more reasonable, consensual leader than his predecessor, but his efforts would come to nought when he was toppled by the party room, who felt he wasn't upholding National values. The new new Premier, former Police Minister Russell Cooper, decided the best course was to stoke an American-style culture war, running ads that argued decriminalising homosexuality would lead to "a flood of gays" crossing the border from NSW. It didn't really stick, and the Nationals would, in fact, lose the 1989 general election in about as big a landslide as the electoral law permitted.