TWO months before the 2005 election the then-leader of the Conservative Party, Michael Howard, made waves by allowing candidates who wanted Britain to leave the European Union (EU) to say so in their campaigns. Today that news would not cause a ripple. On May 12th Michael Gove, the education secretary, and Philip Hammond, the defence secretary, declared that they would opt to quit the union in any immediate referendum. That two loyal and cerebral ministers voiced views once considered outlandish in mere parliamentary candidates shows how much more Eurosceptic the party has become—and that the latest of its perennial debates over Europe strays into uncharted political territory.

The drama dates back to January, when, in a long-promised speech, Mr Cameron pledged that, if granted a full majority at the 2015 general election, he would renegotiate the terms of Britain’s membership and offer voters an in-out referendum. The gambit followed months of bellyaching by Tory backbenchers. The prime minister hoped that the speech would halt the rise of the UK Independence Party (UKIP), which wants Britain to leave the EU as soon as possible, and curb the pressures on his leadership from malcontents. For a short while, it did. Daniel Hannan, an MEP hostile to the EU and all its works cheerily declared it “the most Eurosceptic speech ever by a British prime minister.”

But the honeymoon was brief. Within weeks, MPs were demanding legislation in the current parliament to guarantee the referendum in the next (a measure opposed by Mr Cameron’s pro-European coalition partners, the Liberal Democrats.) Under Nigel Farage, its beerily charismatic leader, UKIP exceeded expectations by pipping the Tories to second place in the Eastleigh by-election in February and securing a record 23% of the vote in local elections on May 2nd. Then Nigel Lawson, an influential former chancellor of the exchequer, further inflamed the debate by calling for Britain to leave the EU.

Thus emboldened, on May 9th two inveterate Tory troublemakers tabled an amendment regretting that the government’s agenda for the upcoming year did not contain a bill legislating for a referendum. In a tacit admission of weakness, the prime minister declared himself “relaxed” about MPs and even junior ministers supporting a move critical of his approach. Comments by Mr Gove and Mr Hammond, whose willingness to contemplate leaving the EU (though neither ruled out a successful renegotiation) were also distinctly unhelpful.

As support for the amendment grew, Mr Cameron’s authority over his party looked shaky indeed. To defang the risk, Downing Street published a draft bill guaranteeing an in-out referendum and invited Tory MPs to initiate it from the floor of the House of Commons (circumventing Lib Dem resistance). Although the parliamentary arithmetic means the bill is highly unlikely to become law, the attempt appeared to please the party. Douglas Carswell, a hardened Brussels-basher, proclaimed that: “We [Eurosceptics] are winning.” Such boasts should however concern Mr Cameron. His speech in January was a gamble that he could marginalise the implacables who simply want to leave the EU by rallying the majority of the party around a referendum acceptable to most members. That manoeuvre has presented two problems.

The first is that the implacables are more than a fringe group—Tim Montgomerie, a Conservative commentator, reckons they now constitute about a third of the party—and they are becoming more combative, not less. Some even want Mr Cameron to dissolve the coalition if the Lib Dems do not agree to formal referendum legislation.

Second, in his attempt to unite disparate views, Mr Cameron left big questions unanswered. Speculation and false expectations have filled the vacuum; on the matter of legislation, for example. Before the local elections the prime minister hinted that he was “prepared to consider” the enabling bill that many of his backbenchers craved. That they redoubled their efforts to obtain one in the following weeks was no coincidence.

Mr Cameron’s plans for renegotiation remain similarly unclear. Lord Lawson judged that any changes would be “inconsequential”. Now MPs want evidence to the contrary. Tim Bale, an expert on the Tory party, says this agitation and Mr Cameron’s attempts to keep his options open invite comparisons to John Major. During his premiership in the 1990s, the Tories descended into bitter infighting. Now, as then, the party is more obsessed about this matter than voters, who are focused on the economy and living standards. And now, as then, the dent to the prime minister’s authority could be lasting (despite the publication of the draft bill, 116 Tory MPs backed the amendment in a vote on May 15th, implying a lack of trust in Mr Cameron’s ability to deliver a referendum). Doubt extends far beyond the issue of Europe. In the same week a group of MPs announced that they would also seek a referendum on gay marriage, currently making its way through the legislature.

The sole comfort for Mr Cameron is that the Labour Party looks divided, too. Ed Miliband, its leader, opposes a referendum on the EU but faces internal pressure to show that he trusts the electorate to make a choice. The Lib Dems are in a similar quandary. So Mr Farage, who appears to be setting the agenda, is the only one with much to laugh about. He has no MPs in the House of Commons, but Mr Cameron’s unruly backbenchers are proving useful enough as it is.