The Conservatives want to repatriate certain powers from the EU
If David Cameron becomes prime minister he may spend an awful lot of time in Brussels as well as talking about Europe.
It is a tricky and potentially dangerous topic for the Conservatives, but the handful of policies that have been announced suggest it could blow up into one of the big stories if Mr Cameron makes it to No 10.
The Irish "no" to Lisbon raises even more tantalising possibilities.
The Conservatives are clear they do not want to leave the European Union, but have very severe doubts about the way it is being run at the moment.
Mr Cameron has made two firm promises - to take back certain powers from the EU and put his party at the forefront of forging a brand new European political group.
But more oblique hints suggest he could also be heading for a first-term referendum on Britain's relationship with the EU.
That's an awful lot of the "E" word for someone who was elected leader promising not to "bang on" about Europe.
It is a subject that evokes real passion in the hearts of many Conservative stalwarts.
That can make it an awkward subject too, where pragmatism is seen as betrayal and principle as obsession.
The Conservative civil war was about Europe, and it was a huge factor in Margaret Thatcher's downfall and the undermining of John Major's government.
Lord Heseltine remains a keen Tory supporter of the EU
But times have changed; the pro-European generals, like Ken Clarke and Michael Heseltine, may not have quit the field but they no longer command big battalions.
The vast majority of those on the Conservative benches now range from being suspicious of the European Union to downright hostility.
They think this is a mirror image of the views of the British voters.
Lower down the ranks, while few openly advocate leaving the EU, many see a semi-detached relationship as a logical outcome.
Most Conservatives think the Irish rejection of the Lisbon treaty is a gift.
While it helps them argue the case that the treaty is dead, it also hands them a convenient blunt weapon for next year's Euro elections.
The June 2009 elections for the European parliament will be taken by most in Westminster, and perhaps many in the country, as merely a dress rehearsal for the general election.
But there is also likely to be clear blue water between the main parties on Europe itself.
David Cameron and Gordon Brown clash over the Lisbon treaty
It is now certain that if the Lisbon treaty is still in limbo the Conservatives will offer a referendum if they win the next election.
What if the Irish do vote again, and do vote "yes"?
The shadow foreign secretary William Hague argues: "If this treaty is ratified in this country without a referendum and if it is ratified in all other countries and comes into force before a general election, in our view not only would political integration have gone too far but the treaty would lack democratic legitimacy in Britain.
"So, as we have already made clear, that situation would not be acceptable to an incoming Conservative government and we would not let matters rest there."
What precisely this means, the Conservatives will not say at this stage. But it sounds like a pretty big hint that there will either be an attempt at renegotiating Lisbon or a referendum on Britain's relationship with the European Union, or a combination of the two.
It is just about possible to see other EU countries allowing UK opt-outs on social and employment law.
It is approaching the fanciful to expect countries such as France and Germany to allow Britain to opt out of a treaty that has already been ratified.
But if there had been a referendum in Britain that instructed the government to seek a different relationship, they would have to accept it, at least in some form.
CONSERVATIVES AND THE EU
1973: UK joins the European Community under Tory Edward Heath
1984: PM Thatcher wins UK budget rebate from EC
1990: Chancellor John Major oversees membership of Exchange Rate Mechanism (ERM)
1991: PM Major negotiates opt-outs to Maastricht treaty
1992: Sterling drops out of ERM on "Black Wednesday"
1993: Major sees Parliament ratify Maastricht, despite Tory scepticism
It is hard to see whether this would end up with new opt-outs, a new relationship, an exit strategy or a reconstruction of the whole European project.
Some think the latter is possible. In the words of one enthusiast, the Conservatives would "storm the citadel" and lead a Europe-wide movement that would change the European Union into a more democratic, looser, organisation no longer aimed at "ever greater union".
But there is a potential downside.
On the Conservative Party's main web page on policy there is not a single mention of Europe, a reflection of the high command's belief that while people might agree with them about the EU, it is not a main priority for most voters.
If Mr Cameron does make it to No 10 and ends up "banging on" about Europe - fighting a referendum campaign potentially against a new Labour leader who would be seeking to make a mark - it might rather bore the voters, who thought schools and hospitals were Mr Cameron's priority.
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