Big two should perhaps 'lance the boil' and let Sinn Féin govern - then fail on its promises

Both Mr Martin and Mr Varadkar will point to massive differences in economic policies between their parties and Sinn Féin. Sinn Féin is also accused of making wild election promises on reducing the pension age to 65, taxing the wealthy, and bringing in a rent freeze.

And then there's the obvious - Sinn Féin's long association with the Provisional IRA and its decades-long campaign of murder and mayhem. Ms McDonald may deny it, but Fianna Fáil and Fine Gael made much play of claims that shadowy figures in Belfast still pull the strings in Sinn Féin.

And incidents like Waterford TD David Cullinane shouting "Up the 'Ra" at a private post-election party do nothing to improve Sinn Féin's image among political critics that view them as apologists for IRA terror.

There simply aren't the numbers for Ms McDonald to lead a government of the left and Fianna Fáil and Fine Gael have ruled out a deal with Sinn Féin.

Such is their horror at the prospect of coalition with Sinn Féin they may even be on the cusp of patching up their century-old differences and doing a deal themselves.

Optimists in Fine Gael suggest another stint in government - even with the old enemy Fianna Fáil - could see Mr Varadkar's party finally benefit from efforts to tackle the housing crisis once supply kicks in.

The argument goes that Sinn Féin's surge in support was largely to do with young people frustrated by high rents and an inability to save for a mortgage and the boost for Ms McDonald's party will evaporate when the situation improves. Of course a failure to deliver greater progress would see Sinn Féin's support rise further.

One of the main fears in Fianna Fáil of going into government with Fine Gael is that it would allow Ms McDonald to be the main opposition voice in Leinster House, further improving her party's chances in the next election. There is another view in both Fine Gael and Fianna Fáil among politicians who could be categorised as the 'let them at it' brigade.

This is typified by Fianna Fáil's Barry Cowen, who this week said his party didn't get a mandate for power and Sinn Féin "need to take their ambition seriously now and ensure we get a government from the left".

It's echoed in Fine Gael by one senior source who said Sinn Féin should be allowed go into government and "see what it can do".

This isn't exactly a generous offer. There's a belief by Sinn Féin's opponents that they would soon come unstuck when faced with the realities of governing.

How would they deliver on its promise to cut the pension age to 65 when faced with a potential black hole in the Social Insurance Fund?

Tens of thousands of social homes can't be built overnight and taxing the wealthy to fund big pledges could scare off foreign investment.

Sinn Féin did not win the election as has been claimed. More than 75pc of people sent their first preference vote elsewhere.

But the support it did get shows there are hundreds of thousands of voters prepared to ignore the party's disturbing history amid dissatisfaction about problems in health and housing. This trend will only grow as the atrocities of the Troubles fade in the collective memory.

Sinn Féin is back in power in the North and it is only a matter of time before it will have the numbers to go into government in the south.

Perhaps it's time for Fianna Fáil and Fine Gael to "lance the boil" and let Sinn Féin take the reins in some form of minority arrangement. For once, Sinn Féin could get caught out on its policies rather than its past.