Writing in the Belfast Telegraph on January 22, I suggested Sinn Fein's performance in recent opinion polls raised the possibility the party might be required to prop up a Micheal Martin government in three weeks time.
Would Martin be phoning McDonald if that circumstance arose? Of course he would... irrespective of what he has said previously about his personal distaste for a coalition involving Sinn Fein... such a deal would raise huge concerns within unionism, which fears that any coalition/propping-up arrangement with Sinn Fein would require some sort of quid pro quo on Irish unity and an early border poll. It is too early to know if a Sinn Fein/Fianna Fail coalition is actually a serious runner, yet one thing is definitely clear at this point: Sinn Fein has made a hugely significant political/electoral/psychological breakthrough and now holds a number of very important cards.
That will spook unionism, not least because it viewed Martin as not particularly interested in a border poll anytime soon, meaning they saw him as the one southern leader they could probably work with.
If he cuts a deal with McDonald, then their room for manoeuvre and negotiation with Martin becomes severely restricted.
So, how should unionism respond? What it must not do is opt for petulance and blame elements of the southern electorate for stupidity.
Sinn Fein's vote seems to be largely a young base which isn't interested in the party's past and will, consequently, turn a deaf ear and blind eye to any criticism of the party from unionism.
And it's also worth remembering that unionism, generally, hasn't made a serious effort to have its voice heard south of the border, even after the Good Friday Agreement.
Sinn Fein will continue to prioritise the 'unity project' and may even make support for any new coalition dependent on the other partner prioritising it, too. Given opinion poll evidence that a growing majority in the south is registering support for Irish unity (although they don't appear to be in a huge rush for it), it is also possible that the Irish political establishment will begin to look at the issue more seriously than it has ever done.
Fair enough, Sinn Fein hasn't recorded a massive victory and McDonald won't be Taoiseach in a few weeks, but when a party wins more votes than what were once the 'big two' parties and its bedrock policy is Irish unity, then it's not unreasonable to imagine that those other parties might begin to give more attention to the unity issue.
I can understand why party-political unionism has chosen not to talk to Sinn Fein about unity (although that still doesn't explain why unionism doesn't seem to have bothered having an internal conversation of its own to list and discuss possibilities).
But if unity is now of new and particular policy interest to Fianna Fáil and Fine Gael, it is essential that unionism talks to someone. It is essential that it sets out its case. It is essential that it wins and influences friends anywhere it can find them.
Yet I'm already hearing some unionists say that this result is a mere blip; that Sinn Fein will be hammered at the next election; that Fianna Fail and Fine Gael have no interest in a border poll; that the Irish electorate don't want the hassle of unity; that the south 'couldn't afford us'; that a majority in Northern Ireland would never swap the NHS, for instance, to have to pay for health care and GP appointments etc.
Yes, maybe all of that is true. But what if it isn't? Can unionists really afford to sit it out and allow the debate to be conducted without any input or advice from them?
And it's not just in the south that unionists need to reach out and find new friends.
They must find them across the UK, too.
A few weeks ago it was assumed - with some justification - that Sinn Fein feared an election, which is why it returned to the Assembly. Would it, I wonder, still fear an election?
Historic is overused as a word, but it doesn't take a final tally of seats to appreciate that this election in the Irish Republic has been groundbreaking, with Sinn Fein's share of first preference votes finally going ahead of the two parties who've taken turns to rule the country for the past 100 years.
Republic of Ireland
While the sounds of Sinn Fein’s Paul Donnelly win rang out and supporters sang the Irish song “O Ro, se do bhath abhaile” which translates as “welcome home”, Fine Gael party hacks and supporters could only look on enviously.
Republic of Ireland
Sinn Fein leader Mary Lou McDonald has said she wants to become Taoiseach leading a government without Fine Gael and Fianna Fail following a strong election for her party in the Republic of Ireland.
From late autumn last year, when it looked increasingly likely that Leo Varadkar was planning an early election, most of us in the commentary business concluded that Sinn Fein would be fairly keen to see the Executive and Assembly rebooted and back in business before that election.