The classic “radical Greens are holding us to ransom” trope has been a staple of the News Limited tabloids over the years but nothing could top the Herald Sun‘s effort yesterday, which had the party miraculously emerging with the balance of power in Victoria after Saturday’s Altona by-election.

State politics reporter Matt Johnston quoted data crunched by dumped ALP state secretary Stephen Newnham, linking the 12.2% swing to the Liberals with Greens triumphs in Melbourne, Richmond and Brunswick. Johnston had specifically commissioned the “hung parliament” research, which ran to just two pages, in advance of Saturday’s result.

Other analysts were wondering what the experienced operative could have been thinking. Notwithstanding the double hurdle — the Greens would need a 3.5-5.5% swing towards the opposition and victory in two out three inner-north marginals — the leap of logic just doesn’t stack up.

According to Newnham: “The Altona by-election result raises the possibility of a sufficient swing against the Government for the coalition to win nine to 10 seats from Labor and for the Greens to pick up two to three seats from Labor. Under this scenario there would be a hung parliament with neither Labor nor the coalition having a majority in their own right.”

The reasoning goes like this. The “tide has turned against the government”. Therefore, the “swing is on”. Therefore, because “the average swing when the swing was against the government” between 1992 and 2006 is 3.92%, the Greens are poised to bag any seat in which the ALP’s margin approaches that threshold, namely Melbourne (2.02%), Brunswick (3.64%) and Richmond (4.88%).

But the “average swing” measure makes the strange assumption that there are two distinct types of election — depending on which side of zero the swing happens to fall — and uses a paltry four benchmarks, the 1992, 1996, 1999 and 2006 state polls. A swing of 3.92% in November would leave Labor with about 50.5% vote on a two-party preferred basis, which no published opinion poll has indicated.

More crucially, the idea that a historic two-party preferred swing will automatically favour the Greens is like saying that all swinging voters are motivated by the same factors. Close another punk rock squat in Melbourne and Bronwyn Pike might be in trouble. Close something like that in Altona, with the requisite Herald Sun take on the potential for “alcohol fuelled violence” and the ALP vote would probably rise.

The issues in Altona — law and order, hoon drivers, the cost of living — bear little resemblance to what is going on over in the inner north, where Greens defectors are made up almost exclusively of frustrated affogato aficionados at the far left of the ALP. In other words, the “swing” against the government in Altona is of an entirely different type to the one that might be recorded in the inner city.

You’d think Newnham would be safer ground when he talks about the Greens increasing their vote by “25%” in Altona from 8.42% in 2006 to 10.43% on Saturday. But the figures just can’t be interpreted that way. According to ABC Elections analyst Antony Green, “changes in party vote are always expressed as a percentage of the total vote, not a percentage of the party vote.”

“So if the vote for Party A went from 10% to 15%, it is a 5% increase, not a 50% increase. That is because you are measuring the proportion of people who switch to Party A, which is 5%.”

The increase in the Greens’ vote was 2.01%, not 25%.

Even on Newnham’s flawed “percentage of the party vote” measure, by-election data from the last ten years show the Greens’ vote has increased by an average of 39% when it was contested by both major parties. The 25% figure invoked by Newnham is in fact modest by historical standards with Altona providing no indication the Greens will do unusually well at the state election.

In fact, there was little evidence that the Greens did very well at all on Saturday, with the anti-government swing captured almost entirely by the Liberals. According to Green: “the fall in Labor primary vote, the rise in Liberal primary vote, and the two-party preferred swing are all about the same value, 10-12%. That’s why I say the swing from Labor has gone straight across to the Liberals without dalliance in other parties.”

“There is nothing in the Altona numbers that screams out left protest vote deserting Labor for the Greens. But in this case there was little difference between Labor’s loss of primary votes and the two-party swing, so I interpret those numbers as mainly a straight swap from Labor to Liberal.”

Interestingly, the Greens may have themselves been partially responsible for the balance-of-power angle. Two weeks ago at a doorstop, upper-house rabble rouser and good bloke Greg Barber told Ten News he was on track to hold the balance of power before promptly Tweeting about it. And even if the Greens vote had ballooned, the prediction of a hung parliament is a ridiculous one.

Veteran political analyst Brian Costar told Crikey: “Predicting a hung parliament in a preferential voting system is like predicting a tie in the AFL grand final. What does Altona mean for the Greens’ prospects in November? Absolutely nothing”.

So rather than a resurgent Greens or a hung parliament, should Victoria be preparing for a new era of Liberal rule? That’s also, it seems, unlikely.

On his blog, Green details a slew of by-elections where third-term state Labor governments have been punished but later bounced back to triumph at the poll proper. The Kennett government’s loss of Gippsland West (12.9% swing) and Mitcham in 1997 (15.8% swing) are sometimes regarded as a canary down the coalmine for Steve Bracks’ 1999 victory. But it’s less widely recalled that the ALP came perilously close to giving back Mitcham in 1999, with Tony Robinson forced to preferences. Those by-elections were a warning, but that warning was muffled come polling day.

In Altona, the Liberals did well because Labor had so many votes to lose, combined with an awful media week leading up to the poll that included a blizzard of negative coverage over Indian students, Noel Ashby’s acquittal, MYKI stuff-ups and a fuel leak at Altona’s Mobil refinery. The sort of issues, not coincidentally, that have been relentlessly drummed up by the Herald Sun. Although undoubtedly a rebuff, a 10-12% swing was still regarded as being on the “outer edge of acceptable”, according to ALP insiders.

Rather than ludicrous predictions of a hung parliament or an unlikely Baillieu victory, the most reliable election indicator remains polls that put the swing against the government at about 4%.

The ALP may well end up losing the inner city to the Greens and parts of the mortgage belt to the opposition in November. But the result of a western suburbs by-election and a Herald Sun scare campaign nine months out from polling day won’t have much to do with it.