Nothing characterises the ancien regime in Leinster House like a carve up about who gets to be Taoiseach. In a bid to stitch together a Frankenstein’s Monster government, the proposal doing the rounds at the moment, according to media reports, is that Fianna Fáil and Fine Gael will rotate the top job.

It almost goes without saying that a ‘coalition of equals’ between Micheál Martin and Leo Varadkar – ‘Maradkar,’ if you will – is completely unworkable. You cannot job-share the highest offices of state.

A sustainable coalition government needs a single main party augmented by a smaller party or parties. Complementarity, not equality. That way, you establish clear boundaries, agree a joint-programme and hive off specific areas of government for either party, but leave it clear that the shots are ultimately called at the centre.

Amid all this power-grubbing, it’s easy to overlook the fact that the recent election was only held because the previous confidence and supply arrangement, with Fianna Fáil propping-up Fine Gael, was unsustainable. Extending the arrangement fulfils Albert Einstein’s famous definition of insanity: doing the same thing over and over and expecting a different result each time.

If it does come to pass, however, the amount of time absorbed by day-to-day management of the coalition will neuter its ability to get much done. Every decision will be tortuous. Who gives way when either side has equal billing?

There’s also an unhappy recent precedent. The Labour Party learned a painful lesson that coalition politics can see the blame unevenly distributed after it helped to drive through Enda Kenny’s austerity measures. The experience has virtually put paid to the party. If the Greens are now crazy enough to join FF and FG in a ménage à trois administration, in order to boost its parliamentary arithmetic, they will find themselves suffering the safe fate.

Sinn Féin, meanwhile, is well-practiced at the long game. The impressive momentum Mary-Lou McDonald built-up in the days following the election, through a series of packed public meetings around the country, demanding her party’s mandate as the winners of the election translated into talks about entering government, has dissipated because of the coronavirus emergency.

She will recognise that if their stunning breakthrough doesn’t now lead to a spot in government, then they are well set to do so next time around. Meanwhile, a spell in office will force FF and FG to cannibalise each other, with Sinn Féin colonising the red/green space in Irish politics and forcing a more familiar right/left alignment in the process.

Making sense of the election result and dealing with coronavirus crisis should have led to the same place – a government of national unity and a fresh election later in the year.

But as Denis Healey wryly observed, turkeys don’t vote for Christmas. To preserve the cartel politics of the 20th Century and to maintain the cordon sanitaire stopping Sinn Féin getting anywhere near power, the two old parties want to close a deal as quickly as possible in case the argument for a temporary unity government gains traction.

If Sinn Féin did enter government – even as a temporary measure to help get Ireland through the current emergency – then a benign precedent would be set, making it impossible to depict them as the bogeymen of Irish politics ever again.

So, a joint agenda is being eked out by the FF-FG backroom teams. All it will do, though, is make the emergence of a Maradkar government look more like the dying jerks of the Irish body politic than a sustainable new administration.

One last gasp for the old parties; one more heave for the Shinners?