THIS week David Cameron, Britain’s newly re-elected Conservative prime minister, will publish a bill to authorise a referendum on Britain’s membership of the European Union. The plan is to hold the referendum before the end of 2017, although some are talking of advancing it to late 2016. Before it can be held, however, Mr Cameron wants changes to the terms of Britain’s membership so that he can present voters with a choice to stay in what he calls a “reformed EU.” But exactly what changes does Mr Cameron want?

So far Mr Cameron has been vague, but he is expected to set out more details at an EU summit in late June. So those seeking the answer now have been reading through past texts in which Mr Cameron set out some demands: the Bloomberg speech of January 23rd 2013, when he first promised to hold a referendum; a subsequent article in the Sunday Telegraph; a later speech on immigration and benefits; and the Conservative election manifesto.

From these sources, analysts have come up with six main demands. First is a four-year bar on benefits, including in-work benefits, being claimed by migrants from the rest of the EU, to stop “benefits tourism”. Second is a reduction in EU regulation and even a repatriation of some regulatory powers from Brussels. Third is a big effort to complete the single market in areas like services, digital and energy markets. Fourth is a mechanism to safeguard the interests of non-euro countries from the risk that an integrated euro zone might discriminate against them. Fifth is a British opt-out from the treaty commitment to “ever closer union”. And sixth is a bigger role for national parliaments in blocking proposed EU legislation.

This list leads to three further questions. Can Britain win the unanimous agreement of other governments? Do any of the changes require treaty amendment, which is hard for some other countries to do? And will they persuade British voters to stay in the EU? The answer to the first is that most of the changes are quite modest, so they should not be too difficult to agree. The second is harder, since at least three of the proposals—the benefits change, an opt-out from ever closer union and a mechanism to safeguard non-euro members—could require a new treaty to guarantee their effectiveness. There may be scope for a legal fudge that stops short of full treaty change, similar to protocols adopted in the past to satisfy Danish and Irish demands after their voters rejected previous treaties. Or there could be a “post-dated cheque”: a promise to incorporate changes into the EU treaties whenever they are next revised, for instance if a new country joins the club. The third question is the biggest unknown. But Mr Cameron is gambling that, fresh from his unexpected election victory, he can persuade voters that it is better to have the devil they know than the devil they don’t. After all, a similar tactic favouring the status quo worked in the Scottish independence referendum last September—but it was a close-run thing.