Bowing to pressure from “euroskeptic” MPs, Cameron this week announced a bill outlining the terms of the proposed referendum. Because of Lib Dem opposition the bill won’t form part of the coalition’s legislative program, and it has only a slim chance of becoming law. But the Conservatives hope that, by forcing Labour and the Lib Dems to vote against the bill, they’ll be able to campaign in 2015 as the only party giving Britons a say on Europe.

The move wasn’t enough to stop more than 100 Tory MPs voting on May 15 from expressing “regret” that a referendum bill wasn’t official government policy, in what was seen as another sign of Conservative divisions over Europe and a setback for the prime minister. And neither is it enough for UKIP, which is demanding a referendum before the next election.

But UKIP’s position is not without risks of its own. The party’s colorful and combative leader Nigel Farage knows that as things stand, the more success he enjoys, the more likely it is that he’ll cost the Conservatives the election, thereby killing off any chance of a referendum. The Labour party, while not as fanatically pro-Europe as the Lib Dems, is fully committed to keeping Britain in the EU.

The obvious solution for both the Conservatives and UKIP would be some kind of electoral pact. However, Cameron has insisted there will be no such arrangement. Farage, for his part, says he’s open to a deal with the Tories, but only if the party dumps Cameron and replaces him with a leader more sympathetic to UKIP’s position. In 2006 Cameron famously referred to UKIP as “a bunch of fruitcakes and loonies and closet racists,” and although he’s walked back those comments as UKIP has gained in popularity, there’s no love lost between the two leaders.

The only chance of an end to the current standoff would be if the Conservatives were indeed to oust Cameron. That seems unlikely however, and there will come a time late next year when the point of no return will be passed in the run-up to the 2015 election — the point after it would be unthinkable for the Conservatives to ditch Cameron and still have a chance of winning.

At that juncture something will have to give if there’s to be any chance of a pro-referendum government being elected, but neither Cameron or Farage will want to lose face. With an official pact unlikely, grassroots activists on both sides are talking about making informal deals at the local level, with the party that has the least chance of winning a particular seat standing aside to give the other a clear run (while UKIP gets most of its support from former Tory voters, it’s also been taking votes from Labour, particularly in the north of England). It’s even been suggested that candidates could run on a joint Tory-UKIP ticket.

UKIP has always vehemently rejected the suggestion that it’s simply a protest party for disgruntled Tory voters who want to give their leadership a poke in the eye, but who will return to the fold when things get serious at the general election. But even the most ardent UKIPper knows — although you won’t hear them admitting it, at least not yet – that their party has no chance of winning more than a handful of seats of their own. The only certain outcome of a strong UKIP showing in 2015 would be a left-wing, pro-Europe government.

Assuming that Cameron remains as his party’s leader, and continues to throw his party enough scraps to prevent it losing more ground to UKIP, the time is coming when UKIP will have to make a choice. It can stand on principle, make the perfect the enemy of the good, and wave goodbye to any prospect of Britain leaving the EU for at least another five years; or it can help to bring about a Conservative victory, and with it the possibility of a British exit — or at the very least, a looser, trade-based relationship with Europe.

Will the British Tea Partiers follow in the footsteps of their American cousins, and force the Conservatives to return to first principles and to reconnect with their base? Or will they simply spoil the party for the Tories — and for the majority of Britons who want to break the shackles of Europe?