Presumption

The Lib Dems love affair with the EU carries on apace despite their drubbing in the recent election, though no doubt they've convinced themselves that it was simply a protest vote and that come the next election things will go back to normal. Still they've seized on figures drawn up recently by the treasury that show that 3 million jobs would be at risk if we left the EU, leaked despite the fact that the Tory chancellor didn't want them released.
Telegraph.

Danny Alexander, the Lib Dem Chief Secretary to the Treasury, will say that official Government figures show that 3.3 million jobs could be at risk if the UK leaves the EU, prompting a row with senior Conservatives
More than three million British jobs would be at risk if Britain leaves the European Union, an official Treasury analysis has disclosed.
Danny Alexander, the Liberal Democrat Chief Secretary to the Treasury, will today inflame tensions in the Coalition by making public Treasury figures that show Britain’s reliance on the EU.
He will say that Treasury experts have calculated that 3.3 million are connected to Britain’s continues membership of the EU.
It will anger senior Conservatives and comes just one day before David Cameron travels to Brussels for a major clash with EU leaders over the appointment of Jean-Claude Juncker as president of the European Commission.

The question is of course is the risk defined? Bandying words like could and would simply implies that if things go terribly wrong and the EU decides to cut off its nose to spite its face and suspend trading with the UK  then jobs could be at risk. Trouble is, the EU is unlikely to do so as they sell far more to us than we sell to them and they will not want to get into a trade war. The treasury report will be as other reports do giving best, worst and middle grounds and it may be that the best report simply says that things will carry on as they are without the cost of the dead hand of EU bureaucracy upon us. Certainly there may be some jobs that will go, particularly in the civil service, but its hard to define if industrial jobs will go, we may find new markets outside of the EU or our products become cheaper to sell in the EU without their oft stupid regulations on hours and paperwork.
Any argument put forward using words like 'could' and 'would' falls at the first step as it implies that they don't know. I rather suspect Mr Alexander doesn't either yet has seized on a report which on the surface appears to support his position like the old Clegg battle cry of 6 million jobs which has been quietly shelved as people now doubt the EU has done so at all.
I still doubt Cameron and co have the balls to leave the EU, I suspect it will take a little while longer for the dissent amongst the population to filter through to the political classes.
We knew this was a long road when we started, but in the end we'll get there.