For several weeks now the Lib Dems have been making threatening noises about the connection between their ambitions for House of Lords reform and Downing Street’s desired alteration of the boundaries delineating parliamentary constituencies.

Richard Reeves, Nick Clegg’s outgoing strategic advisor, has today given the most explicit warning yet that the junior coalition party would sabotage David Cameron’s pet constitutional change in revenge for failure to whip Lords reform through parliament.

Clegg has decided that he simply cannot be seen to have lost all of his political reforms while allowing the Tories to get theirs through in time for an election. (Besides, the Lib Dems come off worst of all three parties from the boundary changes.) As I noted last week, senior Lib Dems have been briefing that they are confident that Cameron and Osborne recognise the scale of their determination and have offered the necessary reassurances. Tory MPs, meanwhile, do not seem much more cowed by the whips  – but that isn’t so surprising. Downing Street’s inability to read and control the mood in the Conservative ranks is becoming a recurrent theme of this parliament.

It is worth noting too that the Tory leadership is much more wedded to the boundary changes than most ordinary Tory MPs. Many of them will have to be reselected in the newly drawn constituencies, fighting unnecessary battles against candidates from neighbouring seats. They will all be competing to energise demoralised activists, several of whom will be flirting with thoughts of Ukip. The whole process will remind many Conservative incumbents how far removed their Prime Minister is from the mood of the party’s grass roots. That process will be a catalyst for further disloyalty.

Why have the boundary changes become so vital - so very precious - to Cameron and Osborne? Obviously a tweak to the electoral map that could automatically gift the party a dozen or more seats at the next election is a prize worth having. But it says something about the shortage of strategic vision in the Tory high command that they expect to be so reliant on a psephological fix to help them to a majority in the next parliament. The awkward fact for Conservative strategists remains that Cameron and Osborne struggled to beat Gordon Brown, a reviled incumbent, in an election when the left vote was split by disillusioned Labour voters backing Nick Clegg. For all Ed Miliband’s weaknesses as a candidate, he has acquired a higher, plumper cushion of a core vote from Lib Dem refugees. Cameron, meanwhile, hasn’t made much progress in the north or Scotland or among swing voters who considered backing the Tories last time but weren’t quite persuaded.

As I noted in my column this week, Labour focus groups are routinely expressing the view that they thought Cameron would bring a change and are disappointed to discover he just represents “more of the same.” The Tories are in a quiet panic about where to find some deep, un-mined seams of voters. There simply aren’t fat bundles of Conservative voters stuffed down behind marginal constituency sofas that weren’t found in time for the last election.

In other words, Cameron and Osborne need the boundary changes because they are short of ideas to inspire the country and bring about a national swing in their direction. Tory MPs know it and they have their own ideas about what sorts of things the party should be doing and saying to win over the nation - ideas that aren't reflected by coalition policy and definitely don't include House of Lords reform. The fact that the threat of losing the boundary changes is a such a big deal for Downing Street just confirms Conservative MPs’ suspicions that their leaders are adrift, short on imagination or inspiration and weak in the face of Lib Dem blackmail. That is not a recipe for parliamentary obedience.