At their annual party conference, the Lib Dems have been talking a great deal about “red lines”. A dangerous use of language, as the most recent memory in the public mind of the use of a “red line” is Barack Obama’s on chemical weapon use in Syria, which turned out to be a bit of a pale pink squiggle in the end.

And indeed, the party’s leadership has already begun having to row back on the idea that they would refuse to work with a government that would call an EU referendum when in power. Although Nick Clegg has insisted that a future Conservative government in coalition with the Lib Dems would have to be prepared to raise taxes on the rich, stop “beating up the poor”, and would not ignore European Human Rights Court decisions, he has not been as strong on Britain’s position in Europe this conference.

The Business Secretary Vince Cable hinted at a party conference fringe event yesterday that a referendum on Britain’s EU membership would be unacceptable to the Lib Dems, and Clegg has also suggested the same thing in the past.

But there are now reports that, privately, he is looking to shift his party’s position of holding a vote only if there is a “material change” in relations with Brussels. It seems that the Lib Dems can no longer afford to insist that they would block such an undeniably popular policy, for which the Tories have firmly set a date, in another coalition government. The Financial Times reveals that a vote on EU membership in 2017 is “more likely than ever”, because Lib Dem ministers and officials have told the paper that they are “willing to give up their opposition to a referendum if the party were to enter into coalition talks” with the Tories again next year.

Clegg was heavily hinting at this shift in position on the BBC’s Today programme this morning. He insisted, “I am a major advocate of a referendum on Europe”, and that he has been throughout his adult political life. However, he said this would only be if the “rules change” and criticised the Tories’ “arbitrary date” for a referendum, warning that David Cameron's negotiations would only be "synthetic". But it’s clear Clegg is moving towards allowing the Tories their plans. He added that he’s “as hard-nosed as anybody” on new EU migrants coming to Britain and claiming benefits on arrival, which again emphasises a shift in his stance towards the EU.

It’s clear the Lib Dems are looking for a good bargaining position in a future pact with the Conservative party. They could end up with electoral reform in local government, and even another chance to reform the House of Lords. One of the FT’s sources, a Lib Dem minister, highlighted this tactic:

We can’t stop the Tories having their EU referendum, but it puts us in a strong negotiating position. We want them to give us a grand package of constitutional measures in return.

This is further evidence that the Lib Dems are using their conference this year, and the build-up to the general election, for pragmatic positioning rather than an unwavering principled offer. I wrote about fighting for the political centre hardly being an inspiring battlecry yesterday.