So at last the line it is drawn, the curse it is cast… John Howard and Peter Costello are to be merged into a two-headed monster. Every Tasmanian expectant mother’s worst nightmare – a dicephalous teratoid.

The geniuses who run the Liberal Party have apparently decided that we will find this fantastic hybrid more appealing as a compound than either of its components separately. The whole, we are assured hopefully, will be greater than the sum of its parts. Two duds are better than one. Put in such blunt terms the concept seems absurd, and so it is. Desperation has finally unhinged the collective wisdom of the coalition.

Nor can either of the newly united Siamese twins take any comfort from their unexpected agglutination. Apart from the fact that they can barely stand being in the same building together, let alone the same body, each is politically damaged by the forced marriage.

For John Howard, it is a stark and humiliating acknowledgement that his loyal colleagues no longer believe he can beat Kevin Rudd on his own. No matter how he tries to spin it, the reality is that the old cloak of invincibility is now in tatters and the John Howard beneath it is revealed as a potential loser, a husk of his former greatness, a pathetic figure whose time has past and now has to rely on a hated and impatient younger rival for support. Every time the two appear together it will be a reminder that the old man can no longer be trusted out on his own; when he does go solo the question will be where is Costello and what is he doing and saying – surely that matters more than the ramblings of a prospective pensioner who wants to be re-elected only so as he can retire with a shred of dignity.

Costello, meanwhile, will be snarling behind his smirk in the knowledge that he can still not present himself as a potential leader in his own right; joined at the hip with Howard, he must now take joint responsibility for everything that goes wrong and if, as is likely, the government goes down the gurgler, he will be seen as having already lost his first election before even taking the reins.

Costello has described Howard’s new role in the traditional Westminster terms as primus inter pares – first among equals. But the fact is that in spite of the ballyhoo, he is still not Howard’s equal. Unless they decide to sing the policy speech as a duet, a diverting but improbable idea, it will be Howard who delivers it while Costello sits politely applauding in the background. If there is to be a leaders’ debate, it will be Howard who joins battle with Rudd; Costello, if he gets to debate at all, will have to be content with Wayne Swan.

Worst of all, not only is Costello not the Prime Minister, he is not even the deputy; that role belongs to Mark Vaile, the leader of the National Party and a massively undistinguished politician by any standard. On the coalition’s tottery podium, Costello has to settle for the bronze.

But even without these obvious problems, going to the election as some sort of 21st century Janus was always going to be a dumb idea. In the television age electioneering is simply not a team sport.

Labor tried it back in 1980 when there was a perception that the leader, Bill Hayden, lacked a sufficiently purposeful image to combat the towering inferno of Malcolm Fraser. The posters showed Hayden as the middle horse in a troika, propped up on one hand by Neville Wran, the party president and immensely popular premier of New South Wales, and on the other by Bob Hawke, the even more popular president of the ACTU who was about to enter parliament with the avowed intention of taking Hayden’s job. The polls had shown that Hayden was heading for a win, but there was a last minute swing against him. The advertising may not have been decisive, but portraying the leader as someone who needed the support of others certainly didn’t help.

This time around Labor is both more confident and more definite. At the weekend Rudd ran a pseudo campaign launch under the slogan “New Leadership”. Given the shemozzle surrounding his opponents, the line could hardly have been better timed.

The government would obviously like a bit more time to bed its odd couple down before the start of the real campaign, but the pressure is now well and truly on Howard. At the end of this week parliament gets up for the year and the work of the present government comes to an end. Its three year term officially runs out on 9 October, although constitutionally it could continue until 19 January. But there is no earthly reason why it should. If Howard does not call an election next weekend people will be entitled to ask why, and the only possible answer will be that he is running scared.

It’s a bad look for Howard, and perhaps and even worse one for Costello. Some government members are still hoping wistfully that Howard might yet step down and give Costello the real leadership, but it won’t happen: the Rubicon has been crossed, the die has been cast, the bridges have been burned and point of no return has been reached. And of course, Costello has said that he won’t challenge. Given his flawless record of pusillanimity over the past 11 years, there is absolutely no reason to disbelieve him.