The Sinn Fein intellectual (although such a description should be treated as "relative") Eoin O Broin, in an interview, with An Phobail has stated that the Republic’s two main parties and not the DUP are the main "roadblocks" to a "United" Ireland.
Of course, the main roadblock is the inconvenient fact that a clear majority of the population in Northern Ireland are happy enough to continue with the Union... but still, the point being made about Fianna Fail and Fine Gael is one worth considering.
Collins reckons it is the two parties' "fighting electoral" machines, "with all the attendant memories and companionship and privileges" which stops them from getting their hands too dirty in the pushfor the 32 County Nirvana. Perhaps. The introduction of a million or so unpredictable souls onto the electoral roll could cause a threat, I guess, to the present status quo but there are too many imponderables to state that for certain. For example, what would happen to the Sinn Fein and SDLP vote once their ultimate target had been achieved? Why wouldn’t it transfer oto parties preaching normal, non-communal politics? Parties like Fianna Fail and Fine Gael? The Unionist (or "Prod", as it would more than likely become on the destruction of our Union) Bloc wouldn’t be anywhere near large or cohesive enough to make much of a difference one way or another. In other words, in the event of the 32 County state there shouldn’t be too much to fear for the typical FF or FG apparachnik in terms of damage to either their party or personal fortunes.
Yet post the Belfast Agreement, the terminology "pan-nationalist front" has disappeared from even the most ultra of Unionist’s lexicon. O Broin is right, Fianna Fail and Fine Gael are only paying lip-service to the pursuit of what should be their national goal. He and Collins are, however, self-deluded/dishonest in their analysis of the reasons. The roadblock on the road to "Unity" hasn’t originated in splendid isolation- its creation is merely reflecting the attitude and opinion of the wider electorate.
Now, why would that be the case? That's a more uncomfortable question for Republicans to answer.