• The Liberal Democrats have been exploiting tactical voting for years.  Indeed, their breakthrough in 1997 to more than 50 Commons seats was made possible by it taking place on a significant scale, for perhaps the first time in post-war general elections.  They will not be more successful in squeezing Labour votes in most blue-yellow marginals than they have been in previous elections.  There may be more so in squeezing Conservative ones in red-yellow ones, such as Nick Clegg’s Sheffield Hallam consitituency.
  • Labour has gained from tactical voting since 2010 – in opinion polls, anyway.  The mid-term boost in its poll ratings came not from former Conservative voters, but from former Liberal Democrat ones. (There has been little red-blue switching since the last election.)  They also gained from tactical anti-Tory voting more broadly during the Tony Blair era.  Some of that former Liberal Democrat support has leaked away recently to the Greens and UKIP, largely because of Ed Miliband’s weakness and deficiencies.  It might return as May approaches.
  • UKIP will target blue voters in red seats and red voters in blue ones.  The policy incoherence of Nigel Farage’s party is an electoral plus for it, at least while it remains an insurgent challenger to the three main parties.  Blue UKIP, Red UKIP, Grey UKIP – Mark Wallace’s guide tells you everything you need to know.  There is only one obstacle to the party picking up lots of tactical votes where it is a possible challenger: resistance to its appeal among those who don’t support it (which helps to explain why support for staying in the EU has risen).
  • This leaves the Conservatives.  Will they gain from squeezing UKIP and Liberal Democrat votes?  Vote Farage, get Miliband: the CCHQ line shows how much stress it is already putting on winning support back from UKIP.  (Lord Ashcroft argues that this could matter at the margins, and that “with marginal voters in marginal seats, the margins matter”.) How much scope is there for the Party to squeeze what remains of the Lib Dem vote in red-blue marginals in the Midlands and the North – or in seats such as Thurrock in which UKIP is competitive?

There will be no formal deal between any of the parties – which explains why Toby Young has abandoned his Conservative-UKIP election pact scheme, as Harry Phibbs reported on this site yesterday. (I wrote that it wouldn’t work. Toby set out his case in reply.)

However, he had a point – not only about Tory-UKIP switching, but tactical voting more broadly.  Lord Ashcroft’s polling of marginals offers voters more information about individual marginal seats than they have had before.  As Tim Montgomerie has said, they will use it.

A moral of the story is that you don’t have to have electoral reform to have AV, since tactical voting is essentially AV by other means.  There will be a lot of it in May, as England sees four parties – perhaps five – scrapping for votes.  It is a rich electoral seam to mine during the months ahead.