This week’s Spectator has a piece(£) by Toby Young exploring the potential for tactical voting to prevent Ed Miliband becoming Prime Minister.

It accepts the premise that both UKIP and the Conservatives were be fighting against each other in every seat in Britain. Incidentally a YouGov poll suggests that such a pact would lead to a larger Labour majority – that is because many UKIP and Conservative supporters would be unwilling to go along with it. I never thought it was a runner anyway.

Yet that is not the end of the matter. You see while electoral pacts are done by politicians, tactical voting is done by the voters. The two things are different.

Mr Young says:

The most common objection to a Tory-Ukip pact is that neither David Cameron nor Nigel Farage will touch it. So why waste time discussing it?

But a pact doesn’t need to be endorsed by the leaders of either party to work. What I have in mind is something bottom-up rather than top-down. A unite-the-right website set up by members of both parties that tells people who they should vote for in their constituency to keep out Labour and the Lib Dems.

This approach is not entirely novel. Mr Young is standing on the shoulders of Billy Bragg. In the 2005 General Election Mr Bragg urged Lib Dem supporters in Dorset South to vote Labour and Labour supporters in Dorset Mid and Poole North to vote Lib Dem. He added that although a staunch socialist he would be voting Lib Dem in his constituency of Dorset West as the best chance of ousting the sitting Conservative Oliver Letwin. The Daily Mirror published a list of seats giving advice for anti Conservative tactical voting.Mr Bragg and others produced websites where votes could be swapped. One was called “Howard’s End.” There were earlier versions in the 2001 General Election. The ballot papers remained secret, no money changed hands. It was based on trust. A Labour supporter and a Lib Dem supporter in another place simply had to trust each other as the computer paired them off.

Even in the 1997 election when the internet was not much of a force in the London there was plenty of tactical voting between Labour and the Lib Dems. There was a bit of a nod and wink tacit encouragement from the Party machines. Labour and the Lib Dems would undertake negligible campaiging in each other’s target seats. They both stood down in Tatton to support Martin Bell. Tony Blair and Paddy Ashdown were pretty chummy at the time.

So the precedent is well established. How would Conservative/UKIP tactical voting work? Labour have helpfully published their list of 106 target seats – 80 per cent of which are currently Conservative held. Of course Conservatives are not only interested in holding these but gaining 40 in order to deliver a Conservative Government with a working majority.

If any website Mr Young produces bumps up the number of Conservative/Labour or Conservative/Lib Dem marginals to 150 or so that would still leave another 400 seats. Would UKIP be at a particular disadvantage if their supporters in those 150 seats swapped votes with Conservatives in some of the 400? It doesn’t seem clear that UKIP have a worse chance in a safe Labour or safe Conservative seat than in a Conservative/Labour marginal of a Conservative/Lib Dem marginal. Indeed in some of these traditionally safe Labour seats like South Shields and Rotherham they have come a creditable second.

Sometimes we can see Euro Election vote share by each Westminster constituency. If that is provided after the next year’s Euro Elections that would help UKIP identify their top target seats for the General Election. Personally I would be surprised if they win a single seat but presumably that is not the expectation of UKIP supporters.

Furthermore the vote swapping website would allow UKIP’s total national vote share to be unchanged without allowing a Labour Government. Naturally David Cameron would be dismissive and clearly state that he wants everyone to vote for their Conservative candidate. Nigel Farage would be equally dismissive and urge everyone to vote UKIP. Of course Mr Cameron and Mr Farage can express such views. However deference to party leaders is the old politics. The voters will make up their own minds.