Even before the votes have been counted, the idea of a Tory-UKIP pact is already gathering pace. Daniel Hannan has called  for a Canada-style 'Unite The Right' initiative, while Nigel Farage himself has reminded us  that he's willing to consider running joint candidates, with David Cameron the only obstacle. If Conservative losses exceed the 310 forecast by Rallings and Thrasher (the deserved subject of a leader  in today's Guardian) and if UKIP perform as well as predicted, expect Tory MPs to start pushing the idea on Friday morning.
The reason is obvious. In the 1980s, it was the formation of the SDP and the consequent split in the left-wing vote that allowed Thatcher to win successive landslide victories. In 2015, a divided right could bring Ed Miliband to power. At the last general election, there were 21 seats in which the UKIP vote exceeded the Labour majority (one shouldn't make the error of assuming that all UKIP voters would automatically defect to the Tories, but many would), a number that is likely to significantly increase next time round.
It's worth noting, then, that the Conservatives missed a good opportunity to reduce, if not eliminate, their UKIP problem when they chose to oppose the Alternative Vote in the 2011 referendum (as Lib Dem blogger Mark Thompson has previously argued  on The Staggers). The introduction of AV would aid the party by allowing it to win the second preferences of the fifth of Tory voters who have defected to UKIP since 2010 (again, one shouldn't assume that all would vote Conservative, but many would).
When I put this point to Conservatives, they reasonably reply  that they opposed AV on principle; self-interest did not enter into it. But those now advocating some form of pact or tactical voting (as Toby Young does here ) are certainly making partisan calculations.
Of course, even if the Conservatives had campaigned in favour of AV, the voters still might have backed first-past-the-post (although it's worth remembering how decisive Cameron's intervention was). But as they mourn the loss of hundreds of councillors tomorrow, the Tories should take a moment to consider how different their position would now be if Clegg and co. had won the day in 2011.