Conservatives are sometimes accused of living in the past, dreaming of an Olde England untainted by vulgar modernity. That is unfair. Tory curmudgeons who date British decline from the end of empire and the advent of colour TV are a dying breed.

The more apt charge is that too many Tories live in the future. They fantasise about governing beyond 2015, without the shackles of coalition, apparently forgetting that two years of sharing power with the Liberal Democrats and a general election lie between their present position and fulfilment of that dream.

The impairment of Tory perspective can be measured in the difference between two recent episodes in parliament. At Prime Minister’s Questions on 24 January, Conservative MPs roared in lusty approval of David Cam­eron’s pledge of a referendum on Britain’s membership of the European Union, to be held by 2017. Five days later the Tories were spitting in impotent fury as the Lib Dems voted with Labour to bury plans to reconfigure constituency boundaries. The defeat will cost Cameron up to 20 seats.

Given that the EU referendum exists only in the hypothetical realm of a majority Tory administration, Conservative MPs’ joy should have been more confined. Had they focused earlier and harder on the real-world obstacles to winning that majority, they might have heeded Lib Dem threats to trash the boundary changes in retaliation for Cameron’s failure to enact House of Lords reform. The warnings were explicit enough.

There is no hiding the self-interest in the Lib Dems’ boundary sabotage. Killing the reform makes another hung parliament after the next election more likely, which boosts Nick Clegg’s chances of negotiating a second term in government. An even bigger factor is the party’s reliance on local incumbency. Lib Dem MPs are notorious for fortifying their seats and holding them in defiance of national voting trends – a skill made obsolete when constituency maps are redrawn.

The ground-war advantage is especially vital in constituencies where the nearest rival is a Tory – about two-thirds of Lib Dem seats. Senior party figures accept that left-leaning protest voters are irrecoverably lost to Labour, which means surrendering seats in the north, where the Tories are hardly in the picture. Clegg’s fortunes hinge, as one Lib Dem cabinet minister puts it, on “protecting our guerrilla bases in the south”.

Ed Miliband would much rather see the Lib Dems hold those redoubts than have them fall to Cameron’s forces. Labour will not waste campaign resources meddling in Blue-on-Yellow battles. (Intriguing insight into how those skirmishes might play out will be furnished in local elections this May, which will feature a high number of rural contests between Lib Dems and Tories.)

Much depends on whether Labour supporters can be relied on to vote tactically against the Conservatives, as has usually been the case, or whether the Lib Dems are deemed so contaminated that leftish voters cannot bring themselves, even with clothes peg on nose, to endorse a Cleggite candidate.

Clegg’s team does not claim any advances in rehabilitating his personal ratings. They still put their faith in a shy cohort of voters who believe the Tories have been tamed by coalition and who might reward their local Lib Dem if the alternative is letting Cam­eron’s wilder MPs off the leash.

That message will be harder to transmit with Labour depicting Clegg’s MPs, in the words of a senior Miliband aide, “as accomplices, not brakes” to the Tories’ social vandalism. That is despite a thaw in relations between the two leaders. Witnesses report a markedly more amicable tone in their private conversations. They have collaborated in response to the Leveson report on press standards and in scotching the boundary changes. They have exchanged thoughts on Cameron’s EU referendum gambit, although not to the extent of agreeing joint refusal to match the Prime Minister’s pledge.

Both men are reluctant to have their next manifesto dictated by quixotic Tory MPs and a Europhobic press. They are also keeping their options open in recognition of how debilitating it could be to spend two years fending off the charge that they don’t trust the people to decide their European fate.

The change in mood is not so much a rapprochement as a slow draining of poison. Lab­our shadow ministers have stopped naming Clegg’s defenestration as the minimum price of future collaboration; senior Lib Dems no longer echo Tory taunts about Miliband’s deficient charisma. They do still sneer at Lab­our’s lack of fiscal gumption just as Labour still accuses the Lib Dems of trading their con­science for a ride in a ministerial car.

Miliband’s aides insist that his exclusive focus remains winning a majority. Most shadow ministers I speak to think another hung parliament the likeliest outcome of the next election. The adjective I most frequently hear from MPs on all sides to describe British party politics is “stuck”.

Faced with an impasse in 2010, Cameron took the audacious step of making a “big, open and comprehensive” coalition offer to the Lib Dems. It is hard to imagine that pro­position being renewed in 2015, even if the Tories are still the largest party in parliament. Conservative MPs have tasted coalition and they don’t like it. In the absence of a majority, many would prefer a minority administration.

Meanwhile, their eyes are fixed on a point beyond the present purgatory of power-sharing. They support Cameron only when he makes policy for an imaginary government he doesn’t lead, which makes it harder for him to run the one he does.

Miliband would also have a hard time persuading his MPs to buddy up with Clegg’s party. A crucial difference is that Labour’s attitude towards the Lib Dems is shifting from blind fury to electoral pragmatism, while the Tories have taken great strides in the opposite direction.