Is the Republic really ready for President McGuinness?
Imagine the scene - a lavish white-tie state banquet at Windsor Castle. The guest of honour is announced. "The President of Ireland, His Excellency Mr Martin McGuinness."
As the Queen looks on approvingly, he opens his speech in Irish: "Do Shoilse, athas orm a bheith anseo sa Bhreatain Mhor. Go raibh maith agat as do failte chroiuil roimh la ata inniu ann." ("Your Majesty, I am delighted to be here in Great Britain. Thank you for your warm welcome today.")
If the bookies are right - and they are seldom wrong - the prospect of Martin McGuinness becoming president, if not dining with the Queen at Windsor Castle, is no pipe dream.
The odds are shortening. The unthinkable is fast becoming a possibility.
No doubt alarm bells are ringing in the crusty club rooms of Ballsbridge and beyond. It has to be said that the spectre of a Shinner in Aras an Uachtarain is looming because of the paucity of candidates seeking public office. What a sad reflection on southern society that the contenders for the highest office in the land are so nondescript.
With no big hitters entering the presidential race, the move by Martin McGuinness is another master stroke. But then, nothing should be a surprise any more with Sinn Fein.
Its leadership has jumped through many hoops and performed spectacular somersaults in Northern Ireland, but seeking the presidential office in Phoenix Park requires a different style of political gymnastics.
Accepting the full responsibilities of the post and gaining widespread trust and support in the Republic looks even more challenging than ignoring the statues of Lords Carson and Craigavon at Stormont to sit in the Assembly.
Martin McGuinness may see the Irish presidency as an extension of his role as a power-sharer at Stormont, but there is a world of difference.
The post of deputy First Minister is based on a tenuous and sometimes fragile trust. The post of Irish president has no such parameters.
It is not a narrow political appointment. The trust and respect invested in the office and expected of the occupant place the president on a higher platform.
Like the Queen, the president is above politics; a role model and ambassador, the keeper of the country's conscience, irrespective of class or creed.
An Irish president is largely subservient to the government of the day, just as the Queen is with regard to Westminster. However, Mary Robinson and Mary McAleese have tweaked the rules in the past two decades.
They have exercised their right to speak regularly, to give interviews independently and, on occasion, even courted controversy with what they had to say.
Whoever follows can be expected to do the same and, in that respect, it is hard to see a Sinn Fein president avoiding more controversy.
That said, the Martin McGuinness I first met in the lawless streets of the Bogside 40 years ago is unrecognisable from the man we see today.
He has proved a revelation as deputy First Minister through his relationship with Ian Paisley and now Peter Robinson.
He also has the knack of saying the right things at the right time as, for example, when he described the 2009 killers of two soldiers at Massereene Barracks as "traitors".
An Ulster Presbyterian minister has described him as a great leader.
Even a prominent loyalist leader commends his candidacy for Irish president.
As many questions are being posed, some remain unanswered.
Can a man who helped run an outlawed army be accepted widely as commander-in-chief of the legitimate forces of the state - one of an Irish president's symbolic responsibilities?
Can a man who was jailed by the state and refused to recognise its courts now preside over the formal appointment of its judiciary?
Judging by the reactions of the past week, opinion is sharply divided across this island as to whether he can be that man in an office that, above all others in Irish public life, requires so much trust and respect.
Martin McGuinness, for all his commendable work as deputy First Minister of Northern Ireland, falls short so long as he refuses to come clean about his past.
He may berate the media for its persistence in its questioning of him, but many more people than journalists would like to see the stones turned over and the full truth told.