Future historians will know this week of the election campaign as the week of the statements of the bleedin’ obvious. First, David Cameron says he wouldn’t serve a third term, an idiotic gaffe or a deliberate piece of sophisticated party management, depending on your faith in the capacity of the Tory leader to play the market. Whatever the motive, as a statement of fact it seems self-evident.

Now Alex Salmond, the SNP’s once and future king has been enjoying fish, chips and pink champagne with the editor of the New Statesman, Jason Cowley. From this comfortable redoubt, he has curled another of the balls for which he is famous into the political debate. If the occasion arises, the SNP’s Westminster MPs would vote against a Tory Queen’s speech.

As statements of the obvious go, this goes right to the top of the league of remarks that smack one between the eyes. As it happens, Scottish Conservative MSPs did for three years between 2008 and 2011 support a minority SNP government in Edinburgh in order to keep Labour out, something both sides have now wiped from their memories. But it is a long, long time since the SNP were also known as the Tartan Tories. They never were going to back the Tories over a five-year term.

The politics of the Salmond statement are clear: it is to give permission to Labour voters in Scotland to vote SNP with a clear conscience. They can desert their old party without letting in the Tories at Westminster by the back door. The politics of the Tory response are also clear, and if anything they are even more cynical. No wonder Ed Miliband described it earlier this week as a “conspiracy” to damage Labour.

Grant Shapps, the party chairman, says Alex Salmond’s remarks constitute a threat by the SNP “to undermine a government chosen by the British people”. That is, a vote for Labour in England or Wales is a vote for a government in the pocket of the SNP. This is a useful little twist in its wider campaign against Labour. It is hard to see quite how Tory strategists think it is helpful to any wider political purpose to tell voters in Scotland that they are somehow excluded from a democratic influence over their own government.

And in particular, it is no clearer how it helps strengthen poor, tired, floundering parliamentary democracy if they ignore the first rule of the game, which is the need for the ruling party to propose a programme of government that commands a majority of duly elected MPs. To make my own statement of the bleedin’ obvious, Westminster is not a government only of the English nor only for them, it is the government of all of the United Kingdom.

To emphasise the politics of the Salmond-Shapps exchanges is not to diminish the huge importance of the questions that lie behind them. How should the relationship between Scottish, Welsh, Northern Irish and English MPs elected to Westminster be recalibrated? How should Westminster itself be reformed? What is the best way of finding out what voters really want? Every day of this campaign so far has felt like another desperate plea for a system that promotes a more honest, open and engaging political discourse.

But it is not what anyone is getting. Last week I spent a bit of time in Peterborough, a marginal constituency that left me with the abiding impression that politics as it is practised at the moment has almost nothing to do with the lives that the people there are living. The absurdity of the fight for advantage in the televised debates, the exhaustive choreographing of all of the rivals’ campaigns, the kitchens! It’s not that it was in any way better just to buy the voters a drink and then take them to the polling station, but it might have been more fun.