Labour and Fianna Fáil find a rare reason to be cheerful
Corollary is definitely a "quare" word and could easily be confused with a heart attack. But both the Labour Party generally, and Fianna Fáil leader Micheál Martin in particular, are entitled to the benefits of applying the corollary today.
If the same-sex marriage referendum was only narrowly carried, or even lost, Labour would have got a right pasting.
The same would have happened if Micheál Martin and Fianna Fáil had lost their seventh consecutive by-election as the main party of opposition.
Thus, the consequences flowing from the big win for same-sex marriage, and Fianna Fáil's Bobby Aylward's election in Carlow-Kilkenny, must include a political dividend for both Labour and Micheál Martin.
How much of a dividend, and how lasting, remains to be seen.
The proposition of same-sex marriage was pushed strongly by Labour within the coalition Government.
Party leader Eamon Gilmore, as Tánaiste, warmly endorsed the recommendation of a referendum from the Constitutional Convention in April 2013.
Almost a year earlier, Mr Gilmore publicly endorsed gay marriage. "The right of gay couples to marry is, quite simply, the civil rights issue of this generation and, in my opinion, its time has come," the then-Labour leader said in July 2012.
At the time, his comments were decried as being excessive but weekend events have shown that he was right.
The Labour Party was very prominent in this campaign, especially current leader and Tánaiste Joan Burton.
The depth of activism in the party was in marked contrast at times to the level of, at best, passive support from large sections of their Fine Gael partners.
But opinion polls leave Labour at about one-third of the 19pc historic vote they secured in the February 2011 General Election.
Some hope persists that this referendum can help in the popularity stakes but expectations were not too high as the weekend euphoria wore off.
"It will boost the Labour activists. It's always good to be associated with a campaign and go to a count centre on the winning side," one Labour stalwart summed up.
In the past two decades Labour in government has helped deliver the decriminalisation of homosexuality; the introduction of divorce; and the reform of contraception laws.
They are entitled to political kudos for those and this latest development.
But such things usually do not compare with more direct economic matters.
Carlow-Kilkenny brought scarce good news to Fianna Fáil as the affable Bobby Aylward was elected after a tough campaign.
The boost is far from transformational for the party, which at times appeared bedraggled and divided during the campaign.
But the outcome brings positive lessons for the party.
From the outset, Mr Aylward fought a straightforward campaign addressing local concerns about a two-tier economic recovery on jobs, problems with housing, childcare costs, and rural crime, among other matters.
Bobby Aylward pitched his campaign very well as a local advocate who would fight for local causes.
His campaign had resonance for a solid block of voters and he won. The win brings some relief to the beleaguered Fianna Fáil leader, Micheál Martin, who has taken more than his share of blows since taking in the wake of the economic collapse.
The Ipsos MRBI poll in 'The Irish Times' 10 days ago gave the party a barely noticeable lift of three points to 20pc.
It shows potential for Fianna Fáil, and the three-point decline in Sinn Féin's fortunes will also give their stalwart activists some encouragement.
But the advantage still appears to lie with Sinn Féin in this battle to be the main party of opposition and the coming months will tell us a lot in that regard.
Micheál Martin himself down-played the potential significance of Carlow-Kilkenny but spoke of his party's potential to pick up transfers.
By-election and general election comparisons are always a bit of a stretch. The result raises questions about the convenient scene-setter for the next General Election, as essentially about a Fine Gael versus Sinn Féin battle.
Be very suspicious of that analysis because it is so very neat. And politics is many things - but it is very rarely neat. Sinn Féin are happy with their Carlow-Kilkenny result. But Fianna Fail could well take more seats than Sinn Féin in the general election. That raises many intriguing prospects.