Each man kills the thing he loves - and so it could be with Tony Blair and Europe. The truth is that he could now become a liability to the European cause, provoking otherwise neutral voters to vote against the constitution simply to spite him.
If he achieves a third election victory, he will be faced with turning around a clear Eurosceptic majority against the European constitution in a fast-approaching referendum. The 1975 referendum on Britain's membership of the European Community was won against similar odds and there are reasons for pro-Europeans to believe that it can be done again. New research by MORI for the Foreign Policy Centre shows as many as two-thirds of the electorate are waverers on the constitution, ready to be convinced by argument. As 1975 showed, such voters are ready to be swayed by politicians they trust.
There's the rub. With 60 per cent of the British public calling Blair untrustworthy, uncritical supporters of the PM are as thin on the ground as WMDs in Baghdad. To make matters worse, Blair's ratings are at their lowest among the very groups that he needs to convince.
First, there are the "Tory lost sheep". This 7 per cent of the electorate is certain to vote, and inclined to support the constitution. MORI describes them as "natural Tories" who deserted the Conservative Party in 1997 and fell straight into Blair's arms. Since Iraq, however, they have been immune to his charms, but they are keen on Charles Kennedy.
The second group (8 per cent) are "persuadable sceptics". They, too, are sure to vote, but are inclined against the constitution. Older than the Tory lost sheep, these voters are the sort who mutter into copies of the Sun, Mail and Telegraph (their favoured reading) that the country is going to the dogs. They are not keen on Islington barristers and they are among the few people in Britain who actually prefer Michael Howard.
The third group (9 per cent) are the "old Labour heartlanders" - fed up with the government, and inclined to use any opportunity to give Blair a bloody nose, if they bother voting at all.
Only the fourth group of "swing voters" (11 per cent) are likely to find the Prime Minister truly convincing. Unfortunately for him, this is the most apathetic group. These "Labour loyalists" are predominantly working class; they don't read any newspapers; and they are profoundly uninterested in Europe. They would vote Yes - but probably won't turn up.
What can Blair do? He can't stay silent on Europe: the waverers will not vote unless the government can demonstrate that the constitution matters. But the more the PM personalises the issue, the more likely voters are to take a pain-free chance to vent their frustration, as they did in the 1999 and 2004 European elections, and this time without the risk of seeing Michael Howard waving from No 10.
That does not make the pro-Europeans' cause a lost one. Many waverers will be won over if Gordon Brown and John Prescott are despatched to drum up support in Labour's heartlands, and if Charles Kennedy can take time off from attacking last year's war in Iraq to focus on the next battle over Europe. But above all, what is needed is a senior politician prepared to put Europe above party-political gain, as Roy Jenkins and Edward Heath did in 1975. In November, a candidate for the role will return from Brussels. Chris Patten combines strong commitment to the EU with an appeal to the Tory lost sheep and the persuadable sceptics. As John Major found in 1992, he also knows how to win the unwinnable. Granting the spotlight to Patten may not come easily to Blair, but it would be a greater act of leadership than trying to win this fight alone.
Mark Leonard is director of the Foreign Policy Centre and co-author of The Referendum Battle (www.fpc.org.uk). The views here are personal ones