A curious paradox about next year’s general election is that Euroscepticism may boost the Tories at the polls, but it may also sink them.
The Conservatives are, by many measures, polling well for a government that has pursued some unpopular measures such as austerity.
The Liberal Democrats have been gravely damaged by the coalition, and if anything the Tories have benefitted from this.
The public also seems to some extent to have blamed the Labour Party for much of the economic difficulties of recent years.
These various factors seem to explain why the Conservatives have now been ahead in the polls for months.
A latest poll, taken by Tory peer Lord Ashcroft, shows that the Conservatives have maintained their lead over Labour, even since the humiliation of David Cameron by other European leaders, who ignored his vehement opposition to Jean-Claude Juncker becoming the president of the European Commission and almost unanimously backed the former Luxembourg PM.
The stand-off seems to have bolstered Mr Cameron’s street cred among Eurosceptics.
In normal circumstances, good poll ratings allied to Liberal Democrat disintegration would return Mr Cameron to Downing Street (perhaps with the connivance of a block of MPs such as the DUP).
But the ongoing support for Ukip will surely wreak havoc in marginal Tory seats. Even if only a third of that 15 per cent of voters who currently say they would support Ukip actually vote that way next year, it will deprive the Conservatives of too many seats.
It is hard to envisage an understanding between the Conservatives and Ukip which will stop this happening.
Thus the only one of the three main parties Eurosceptic enough to commit to an in/out EU referendum is the one most at threat from the arch Eurosceptic outsider party, Ukip.