Andrew Lynch: O Cuiv broadside shows Fianna Fail is a family at war
Eamon O Cuiv is the closest thing Fianna Fail has to royalty. The grandson of Eamon de Valera looks and sounds uncannily like his famous ancestor, which is why some supporters have affectionately nicknamed him Dev Og.
So when O Cuiv warns that the Soldiers of Destiny could be facing their "demise", Micheal Martin needs to take him seriously - before the party's morale crisis becomes a full-blown leadership crisis as well.
A striking new opinion poll published yesterday proved Dev Og's point. For the third major survey in a row, the government parties are gaining support and Fianna Fail remains stuck in the doldrums at 17 to 18pc.
In other words, any progress made by the party since its 2011 election meltdown has been frittered away, and a recovering economy means the situation is likely to get even worse.
While O Cuiv may not be issuing a formal leadership challenge, his analysis certainly lets Martin have it with both barrels. In his view, Fianna Fail is suffering from an "absolute collapse of self-belief", with even the grassroots wondering why they bother any more.
Unless the front bench comes up with a radical new plan soon, he claims, it could become "a small niche party" that will "fade away very quickly".
As for the man at the top, O Cuiv's sardonic view is: "The danger, if you decide he is gone, is that you replace Micheal with another Micheal."
To put it another way, there is no point in a leadership election now because we might end up with someone equally useless, which must be a strong contender for the most lukewarm endorsement in Irish political history.
Martin's colleagues might well try to dismiss O Cuiv as a de Valera tribute act, a rural throwback who shares his grandfather's vision of comely maidens dancing at the crossroads.
In this case, however, Dev Og has plenty of people to back him up.
One of them is David McGuinness, the young Fingal councillor so outraged by his failure to secure a Dail nomination for Dublin West that he is threatening to run as an independent - and there are rumours that his move for the exit door could develop into a stampede.
O Cuiv and McGuinness both see the problem in class terms.
They want their party to go back to its roots as an unashamedly nationalist movement that stands up for small farmers and working-class people.
Unfortunately for them, Sinn Fein has been busy cornering that market in recent years while Fianna Fail became known as champions of big business, property developers and the infamous Galway tent.
On social issues, there is further evidence that Martin may be leading his troops in a direction they don't want to go. He has promised to campaign enthusiastically for a Yes vote in the upcoming same-sex marriage referendum, but polls show that Fianna Fail supporters are less keen on the idea than those in any other party.
Senator Jim Walsh resigned over the issue of gay adoption last week, which got marginally less attention than Zayn Malik leaving One Direction but was yet another sign that the party's liberal makeover has left a lot of cracks showing.
All this means that when Fianna Fail gathers for its Ard Fheis at the RDS on April 24, delegates will need something more than just another pep talk. They need Micheal Martin to show that he has at least some concrete policy ideas for how to get out of this mess.
One month later there will be a crucial by-election in Carlow-Kilkenny, and anything less than victory would provoke calls for the Cork choirboy to hang up his hymn book.
Despite O Cuiv's apocalyptic warnings, Fianna Fail is unlikely to die off any time soon. There is even a chance that the party could be in power again this time next year, since on current polling it would be impossible for any two other parties to form a coalition.
Martin is still his team's best media performer by far, and right now everyone on the frontbench looks too jaded or too raw to replace him.
Dev Og has done a good job of diagnosing Fianna Fail's illness.
Even his iconic grandfather, however, might struggle to come up with the right prescription.