When will our political leaders realise that the action they take when dealing with the European Union will have a direct and significant effect on their success at the polls?Looking at lists of the issues people prioritise when it comes to voting in general elections, concern about Britain's relationship with the EU tends to linger some way behind the economy, schools, hospitals and crime.
But politicians make a huge mistake if they believe this means that people don't care about the issue.
The most recent evidence that EU policy can have a critical impact on a party's level of support is the bounce in the polls that the Conservatives appear to have enjoyed since David Cameron last month vetoed EU plans for a 'fiscal union' treaty.
Veto boost
An ICM survey for the Sunday Telegraph has given the Tories their highest rating since last year's general election and a six-point lead over Labour, up from two points before the pre-Christmas summit.
The poll puts the Tories up two points since the start of December on 40%, with Labour support sliding by two points to 34%, opening up the widest margin between the two parties in 18 months.
Other polls have confirmed the trend, with a post-summit BBC report highlighting polls by Ipsos Mori and YouGov that also put the Conservatives ahead of Labour for the first time this year.
Questioning people about the EU summit's outcome exposes the overwhelming public support for the Prime Minister's actions that underpins this poll shift. A Populus survey for The Times showed 57% felt Mr Cameron was right to use the veto while only 14% disagreed and another, for the Mail on Sunday, showed that 62% supported David Cameron's actions, while only 19% said he was wrong to use the veto.
Ed Miliband's response in the immediate aftermath of the summit, accusing the Prime Minister of being "out of touch", couldn't have been more ill-judged.
Poll threats
But this latest shift is far from the first time time polls have reacted sharply to how politicians act on the EU.
When, back in October 2007, Gordon Brown confirmed his support for the Lisbon Treaty and it became clear that he would not extend his party's previous promise of a referendum on the EU Constitution to the revised document, the result was an abrupt end to his honeymoon as the new Labour leader.
Brown actually increased his party's support through the September 2007 eruption of the Northern Rock crisis, when polls showed a three-point Labour lead mid-month widened to nearly eight points by the end of September. Even the events of early October that year, when the Conservatives unveiled a new inheritance tax policy and Brown was accused of having 'bottled' an early general election, resulted in him conceding only a slight lead to the Conservatives.
So far, not so bad for Mr Brown. Until, that is, later in October 2007, when he agreed to the final text of the Lisbon Treaty and made a statement to Parliament on the 22nd of that month. By the end of that week, Conservative support was growing again and Labour's ratings started a precipitous fall, ending the year at a punishing ten point deficit on the Conservatives as Gordon Brown turned up (late) in Brussels to sign the treaty.
The fact that this poll gap then remained broadly the same until late April 2008 shows that Labour's hair-raising fall in public support over a few short weeks between the end of October and mid December must have been due to some very particular event after both the peak of the Northern Rock bank run and the fallout from the party conferences.
It's impossible to dismiss that this was the period during which the deceit of the process of re-naming the EU Constitution as the Lisbon Treaty became crystal clear and Gordon Brown confirmed that he would not grant us the EU referendum we had been promised.
But Brown has been far from alone in suffering at the polls as a result of his EU actions. Later, in November 2009, David Cameron suffered a similar fate when he also dropped his "cast iron guarantee" of a vote on "on any EU treaty" emerging from the negotiations that came up with the Lisbon Treaty.
The Conservative leader also suffered an immediate drop in public support that, as we speculated at the time might turn out to be the case, did indeed re-balance the polls in a way that resulted in Mr Cameron's failure to secure a clear majority at the general election, forcing him to form accede to coalition government.
Arguably, the Liberal Democrats have suffered the worst of all from this trend in public opinion. Languishing in the polls and seemingly looking down the barrel of an electoral gun, the party's leaders still don't seem to realise where they have been going so wrong.
Referendum opportunity
This clear and growing pattern in how EU policy moves public support to an extent that affects electoral fortunes should provide much food for thought for any party aiming to improve its chances of obtaining a clear majority at the next general election.
Obvious focus should be placed on where party policy is at stark odds with public opinion and where better does such an opportunity lie than over whether there should be a referendum on Britain's EU membership?
The Sunday Telegraph's ICM poll also confirms that people do not back Mr Cameron's decision to rule out a public vote on whether Britain should stay in or leave the European Union. A majority of 59% to 25% (pdf, Table 5) say that there should be a proper in-out vote and most (51%) wish to see one in this Parliament.
If one veto, to unknown effect, can deliver a four-point boost in the polls, it's not hard to imagine the electoral rewards awaiting the party that grants that EU referendum.
