In Greek mythology, the Siren was a female who would lure sailors to their doom by singing a song which no man could resist. Some elements in the media are describing Ed Milliband and Nick Clegg's position tonight as akin to that of sailors being dragged onto the electoral rocks by the siren song of a referendum on EU membership from David Cameron.
It's in no small part a triumph for Nigel Farage and UKIP which can be seen as having had a decisive influence on British politics which can't be bad for a party with no seats and only a handful of local councillors.
How then should the rest of the political world respond to Cameron's mealy-mouthed embrace ? After all, what he has basically said is "vote for me in 2015, I'll spend the next two years trying to get some concessions out of the Europeans which I'll fudge into something you can vote for." In short, as I said yesterday, the desperate ploy of a desperate man clinging desperately to power who knows and sees electoral defeat barrelling down the road toward him.
Yes, it's a trap so how could Nick Clegg and Ed Milliband and other anti-Conservatives respond? Basically, there are four options:
1) Match Cameron's proposal - basically say that if there is an alternative non-Conservative Government elected in 2015, that Government will also seek to re-negotiate Britain's relationship with the EU and put it to a similar referendum.
Superficially fine but it lays Milliband and Clegg open to the charge of weakness - that they are merely following Cameron's lead which leaves the Prime Minister as the supreme political figure and the others as also-rans.
2) Oppose a referendum - this is the current Labour policy and is predicated on the notion that since Lisbon and indeed Maastricht were never put to a referendum, there's no reason why a re-negotiated Treaty (if there is one) needs to be.
This offers consistency but falls right into the elephant trap of laying Labour and the Liberal Democrats open to the charge of "not trusting the people" - a powerful charge in any democracy.
3) Do Nothing - I'm a big fan of masterly inactivity and once the furore over this has died down, it will be back to the bread-and-butter issues of the economy and the news on fourth quarter GDP is likley to be fairly dire (as indeed were the recent borrowing and debt numbers) and that will quickly shift attention away from today's events.
Ed Milliband's sole priority has to be winning the 2015 General Election. What he cannot afford to be is diverted by short-term meanderings. IF the economy continues to falter, he will be able to portray the Coalition as a failure and that is his strongest card. A cornered Cameron will doubtless play the Europe card in the election campaign but, as the ever-insightful Mike Smithson on politicalbetting often opines, Europe is well down the list of most people's priorities.
Short-term, masterly inactivity won't be easy but it could pay dividends.
4) Trump Cameron, offer a quicker and more direct referendum - this is what I would do were I leader of either the Labour Party or the Liberal Democrats.
What I would do is put a bill before the Commons calling for a straightforward in-out referendum to be held on May 1st 2014. The proposition would be simple - do we stay in the European Union or do we leave? If the Conservatives try to block or vote against the bill, they could be opposed of hypocrisy. Within the Conservative Party, there would be civil war between those wanting to vote for withdrawal and those trying to hold the Cameron line.
If the Referendum were to take place, what would Cameron do ? Vote to stay in and then offer to re-negotiate if he wins the following election or vote no and join with UKIP?
Referenda, as Nick Clegg will tell you, don't always give you the result you want but it would leave the Conservatives cornered and divided and often the politics is more important than the result.
Cameron has had his day in the Sun so to speak - the economic figures may well cast a much longer and more painful shadow. One thing is clear - today's announcement won't break the Coalition - none of this was part of the initial agreement but it does, I think, make the prospect of a Labour-Liberal Democrat Coalition more of a reality.
The latest ICM poll puts the Liberal Democrats back on 15% suggesting the party COULD hold more than half their seats - far removed from some of the projections of annihilations from those in the blogsphere with an abiding contempt for Nick Clegg.