The ongoing, increasingly personal showdown between Mike Nesbitt and Basil McCrea reminds me of the showdown between David Trimble and Jeffrey Donaldson, which lasted from April 1998 (when Donaldson left the talks process) until December 2003 (when he left the UUP).
The immediate consequence of Donaldson's resignation - and he took others with him, of course - was the final tipping of the scales against Trimble and the onward, upward progress of the DUP.
But there was one very significant difference between then and now: because, back then, the UUP did have a very clear role, relevance, direction and strategy.
And, even though the departure of Donaldson and others was an enormously heavy blow for Trimble and the party, there was still a sense that there remained a purpose for them in local politics.
In other words, there remained a job that the UUP - and only the UUP - could do.
Under Nesbitt's leadership, though, it's very hard to discern what purpose the UUP serves anymore.
If asked to name three specific and very distinct differences between the UUP and DUP (and I'm not counting leadership problems and internal bickering), I couldn't name them.
If asked to explain why you should vote for one, rather than the other, I couldn't tell you. Because, for all intents and purposes, the UUP and DUP are now pretty much the same.
And that probably explains why Nesbitt has fitted so easily into the Unionist Forum and why he has given his personal imprimatur to a series of joint letters, leaflets, statements, meetings and initiatives.
Yet, in steering the UUP into the DUP's waters, he is sending out a message to the broader, pro-Union electorate: namely, that if you want a party to challenge the DUP and serve as an alternative to them, then don't look to the UUP.
He is also sending a message to a key section of his own membership and voter-base: namely, that he prefers cohabitation to confrontation and electoral pacts to electoral challenges.
When Nesbitt was elected UUP leader, it was because he had convinced enough people that he was the 'change' they needed; convinced them that the very act of electing him would turn around the party's fortunes. The opposite has been the case.
In his attempts to look tough, he has picked fights with key people from every wing of the party. Both Ken Maginnis and Fred Cobain, who were key supporters, have abandoned him.
The disputes with John McCallister and McCrea (which could and should have been handled so much better) suggest that he is willing to risk the loss of the sort of liberal/secular/small-u unionists whom he claimed to be trying to reach out to during his leadership campaign, while the cosying up to the DUP and the Orange/unionist unity wing of the party suggests that he has thrown his lot in with them.
If McCrea goes (and probably McCallister), then others will follow. Maybe not high-profile names (although I would predict a couple of 'surprises'), but a steady drip-drip away from the UUP.
And if there is no difference between the UUP and DUP, then why the need to keep up the pretence of two distinct, separate parties?
Indeed, why would anyone join the UUP when the DUP looks so much bigger and better organised?
All of which leaves a huge electoral hole to be plugged. My own view is that people who aren't already voting for the UUP, or DUP, are not going to be voting for them if they get closer together.
People who have voted for the UUP, because they see it as the more 'moderate and secular' of the two, are unlikely to vote for a merged entity.
Those who have opted out of voting are unlikely to opt in because of agreed candidates and identikit manifestos.
The direction Mike Nesbitt has taken the UUP is a direction which will either leave it utterly irrelevant (a process which is well under way, according to two Belfast Telegraph/ LucidTalk polls), or else will, simply and quickly, kill off the UUP altogether.
And that means that an awful lot of unionist/pro-Union types are not going to have a home they are comfortable with.
So, where do they go? Well, it strikes me that there is already realignment under way within unionism. The flags protests indicate that a section of loyalist/working-class unionism is deeply unhappy and in search of new voices and vehicles.
Indeed, I think it's an unwarranted fear of those new voices and vehicles which led the DUP and UUP into setting up a Unionist Forum - in the hope of swallowing up and silencing them. That would be a mistake.
Similarly, the ever-closer relationship between the UUP and DUP (which makes sense if so little separates them) will, almost certainly, encourage the emergence of 'a more liberal grouping', ready to tap into the growing market of disengaged, disconnected voters.
Unionism has nothing to fear from realignment and new parties. Indeed, the reverse is the case.
Unionism itself is a very broad church and it will benefit from a broad array of choices and challenges.