After May’s election, the Lib Dems argued that to stay out of coalition would undermine their arguments for a more consensual politics, and for proportional representation itself. It’s a strong argument, too. If fair votes ever come to Westminster, coalition will be one of the two typical outcomes alongside minority administration, as currently being road-tested by Alex Salmond without the impediment of Tavish Scott. For those committed to power-sharing, like Lib Dems and Greens, it might indeed seem irresponsible not to share power when you’re offered it.

However persuasive an argument that may have been, the specific offer made to them was to go in with ideological state-cutters, and that’s a very different choice. They didn’t decide to work with the Tories because “the numbers made it inevitable”, any more than the Tories compromised because they “felt the hand of history on their gonads, squeezing hard“. They’re working together because the Orange Book Lib Dems have always had more in common with the Tories than with Labour or indeed anyone else. It’s a snug fit, at least for a significant chunk of both coalition parties, and when you look from one to the other it’s already becoming hard to say which is which.

Aside from civil liberties, where the Tories alone were committed to a position significantly more sensible than Labour in any case, the combined result is very consistently right-wing, and it almost looks like they’re trying to alienate their voters. This has been a particularly bad week for the Lib Dems in this regard. Most attention this week has been focused on the tuition fees debacle. Yesterday, the Lib Dems’ education web-page looked like this, but today those commitments have gone. In their place is a page discussing the Browne report and the supposed wins of Vince Cable following it. In passing, to compound my reputation as a grammar snob, it currently also has a typo, like most education press releases.

If you pledge to your voters to abolish tuition fees knowing very accurately what the state of the public finances is, you can’t spin actually increasing them as compromise. Compromise might be a freeze on the current fee regime, plus a bit of wait-and-see on the economy. Abolition postponed. I wouldn’t have supported it, but it wouldn’t have led to the mass outrage at the Lib Dems seen so clearly on Question Time last night.

That issue has been exhaustively covered elsewhere, but it provided a kind of perverse cover for two other decisions which will certainly appall both activists and voters. A cross-party move was made to amend the AV referendum bill to include an STV option, backed by Caroline Lucas, Austin Mitchell and Douglas Carswell. An MP or two from every party sitting in the Commons backed it … except for the Lib Dems. If Tories feel free enough to rebel simultaneously against the coalition document and their party policy on PR, how come not one Lib Dem was prepared to stick to party policy that night? This issue has also been given a good go-over on the blogs, but surprisingly little mainstream media coverage, even from the wonkish political correspondents who could tell you your d’Hondt from your Condorcet.

The third move against Lib Dem party policy by their Ministers this week may, if anything, have been the worst. Their Orange manifesto included a proposal to sell off 49% of the Royal Mail, something all three of the larger Westminster parties have a peculiar desire to do, against both common sense and public opinion. Yet when Vince Cable set out the coalition’s proposals mid-week, that 49% had become 100%, and the Post Office network, scene of so many Glum Councillor-style Lib Dem photo-ops, would be “mutualised”.

I love true mutuals and co-ops. I can’t get enough. Fans owning their clubs. Bring it on. Credit unions. Absolutely. But “mutualisation” of a national monopoly/utility, as also proposed by the Lib Dems for Scottish Water, is just code for privatisation, which is why it’s also Tory policy in Scotland. Along with the plans now for 100% privatisation of Royal Mail, this goes way beyond the manifesto offered to the public by the Lib Dems.

The savagery unleashed on the Post Office and the vote against STV both got buried under the avalanche of criticism over tuition fees. It’s an extraordinary week, in short, one in which their membership may finally have started to realise that their leadership’s apparent lack of any real principles really will risk a complete wipe-out for them. Government approval dropped in YouGov’s tracker by 11% in one day. I assume the Lib Dems noticed.

This administration, the first coalition any English resident below the age of 65 will have lived under, is giving definition to the word coalition in the minds of many. Compromises one can understand – coalitions cannot exist without them – but the sheer volume of betrayals and u-turns are damaging the reputation of coalition politics as a whole. It would be entirely understandable if the voters felt increasingly reluctant ever to elect a coalition again, or indeed to support proportional representation, if it means more of this kind of let-down. It’s an irony, given the claim this deed was done in May to defend the principle of cooperation, and also to reform the Westminster voting system. It may kill both stone dead, along with the Lib Dems.