Tonight at 10.35pm, Prime Time will hold the first of two by-election debate programmes. In a special hour-long programme, 10 candidates in the Roscommon South-Leitrim by-election will take part in a live studio debate hosted by Miriam O’Callaghan.

On Monday 6th October, the Dublin South-West candidates will join David McCullagh to debate the issues in their constituencies. 

Between now and polling day, a great deal of political and media time and energy will be devoted to the two by-elections; the residents of Roscommon South-Leitrim and Dublin South-West will have their votes sought, their views canvassed, and – quite frequently – their dinners interrupted.

From Strokestown to Jobstown, no door will remain unknocked, no baby unkissed, no promise left unmade.

And once the ritual is over, the votes are counted and the winners declared, will any of it have mattered?

The answer is no – and yes.

No, because with the Government's huge Dáil majority, even a double defeat – which is what the bookies expect – will not unseat the coalition.

Also, the trend of the last three decades has been for Governments to lose by-elections, so it shouldn't be beyond the wit of the coalition's spin machine to explain away two losses – though, given the current hames being made of the Seanad by-election, one might wonder.

Until 2011, you had to go back to 1982 for the last Government by-election victory, when Noel Treacy won in Galway East. To date, the Fine Gael-Labour coalition's record has been much better – played four, won three.

True, there were special circumstances in those victories – Patrick Nulty's win for Labour in Dublin West in October 2011 came very early in the Government's term; and the Meath East and Westmeath by-elections saw relatives hold the seats of Fine Gael TDs (Shane McEntee and Nicky McFadden respectively) who were popular and had died in particularly distressing circumstances, so there might arguably have been a sympathy factor.

Still, that's a good record in times of austerity, and on a worst case scenario on October 10th – two losses – the Government will still have a 50/50 by-election record.

And yet – even when Government's have thumping majorities, by-election defeats can have surprising and profound political effects.

Jack Lynch led Fianna Fáil to its greatest ever majority in the 1977 election; just over two years later, twin by-election defeats in constituencies in his Cork heartland precipitated his early retirement as Taoiseach.

After the 1992 election, Labour somewhat reluctantly went into Government with Fianna Fáil, partly because an alternative Rainbow Coalition didn't have the numbers to win a majority in the Dáil. But two by-election victories apiece for Fine Gael and Democratic Left changed the Dáil arithmetic, just in time for Dick Spring to remain in Government after the final falling out with Albert Reynolds at the end of 1994.

A slightly more intangible result of by-elections is the effect on party confidence – and the position of the various party leaders. After all, it was a particularly poor result in Meath East – fifth place, behind Direct Democracy Ireland – which first put the skids under Eamon Gilmore's leadership.

Now the party will be anxiously looking for signs that changing leader has improved its electoral prospects – or at least stopped its decline. A reasonable showing for Labour will be particularly important in Dublin South-West, where the party currently holds two seats out of four.

For Fine Gael the by-elections, particularly in Dublin South-West, will be more about positioning a credible candidate for the general election, though given the current unhappiness in the parliamentary party, a respectable result will be important.

For Fianna Fáil, a win seems like a must. Micheál Martin's by-election record thus far has been pretty disappointing, given that the main opposition party, which hopes to portray itself as a contender for Government, should really be winning seats. Second place simply isn't good enough.

Sinn Féin will also be looking to made a break through, especially given its performance in the most recent Dublin West by-election, which surprised many observers. It will be hoping that Dublin South West will prove fertile territory – anything other than a victory here will certainly puncture the party's self-confidence, and raise questions about the reality of its strong showing in opinion polls.

And what of the other segment showing well in recent opinion polls – Independents and Others? Around a quarter of voters have been telling pollsters they would vote for Independents or Others, and the by-elections are a good test of whether this is accurate, especially as the seat in Roscommon South-Leitrim is vacant due to Luke Ming Flanagan's election to the European Parliament. The problem here, as always, is the sheer number of candidates in this category – unless they transfer tightly to each other, they may fall by the wayside early.

So, whatever happens on October 10th, it is highly unlikely to lead to an immediate change of Government – but it will still offer plenty of interest and, perhaps, portents of things to come.

David McCullagh