Election Editor Graham Dines says voters who wanted a referendum on the European Constitution may not realise how pro EU the Liberal Democrat leader really is

THE only certainty that follows the surge in support for the Liberal Democrats in that Labour will not win the General Election.

And while the odds on an outright Conservative victory have lengthened considerably, any talk of Nick Clegg becoming Prime Minister at the head of a Liberal Democrat government are utterly fanciful.

The perverse first-past-the-post polling system means there is no way the Lib Dems could emerge as the largest party. But it’s little wonder that Gordon Brown gave such an outrageous, simpering performance in the first of the leaders’ debates last week as he sucked up to Clegg with the unwritten message: “Nick, I’m your man after the election. We can go places.”

Brown will do almost anything to defeat the Tories. It was David Cameron who pushed for Clegg to take part as an equal in the debates. His mistake looks set to cost him and the Conservatives dear.

What Cameron needs to do in this Thursday’s debate on foreign and defence policy is to be positive but also go for the jugular over the European Union and the Treaty of Lisbon.

Clegg would frog march the UK into a federal Europe, suborning the armed forced to generals and admirals from Slovenia and Latvia sitting in Strasbourg and answerable to the nice Herman van Rompuy, unelected President of the EU.

Cameron has to hammer home to the watching largely Eurosceptic British voters that Clegg – once a Eurocrat and then a Euro MP - would be an utter disaster.

He has to establish that a Gordon and Nick love-in would destroy what sovereignty we have left in Britain.

But Cameron finessed himself by reneging on the cast iron guarantee that he would hold a referendum on the European Constitution/Treaty of Lisbon. That’s when his credibility started to wane – the Tory opinion poll ratings have not recovered from this broken promise.

The other side of the coin is that Clegg might be able to achieve something which neither Tony Blair nor Gordon Brown showed any interest in attempting – convince the British that the country’s future really does lie at the heart of Europe, that we should join the single currency, and that we should be enthusiastic supporters of the Grand European Project of a federal super state.

If Clegg is to emerge on Thursday evening with his stock still sky high, he is going to have to convince voters that Europe is something not to be feared and that the Little Englanders now in charge of the Tory Party – as opposed to the Conservatives who proudly took Britain into the Common Market in 1973 – would reduce the UK to a fourth rate bit part player on the international stage.

So Cameron’s tactics are clear. He’ll have to withstand the usual accusations that the Tories have put themselves on the margins of Europe by joining with former Nazi and assorted right-wing thugs from eastern Europe in the European Parliament, and turn it to his advantage.

If he doesn’t, not only will the Conservative not mop up the Lib Dem seats they need to win to achieve an overall majority – or to become the largest party in Westminster – but a number of Tory-held constituencies could fall to the Lib Dems.

While election strategists may like the impact on the Tory vote of the Lib Dem surge, Labour candidates in the north of England won’t - in many areas, the Lib Dems are their main rivals and they could find themselves discarded in a Lib Dem advance.

Chelmsford is the main Tory-held Lib Dem target in East Anglia. The party has high hopes in Norwich South, currently held by Labour’s Charles Clarke, while the Tory by-election success of Norwich North could be reversed by a strong Lib Dem showing.

The weekend polls, if repeated on May 6, could increase the number of Lib Dems seats by at least 20. That means that Tory and Labour constituencies not on anyone’s current radar would have to elect Lib Dem MPs.

I’m tempted to say that I’ve heard all this before – Watford was a certain Lib Dem gain in 2001 and 2005, but stayed Labour. St Albans was gained by the Tories, not the Lib Dems, in 2005.

Strephen Robinson, Lib Dem candidate in Chelmsford, says support for him is swelling while Tory Simon Burns reports Conservative strength is as high as ever because voters don’t want five more years of Gordon brown. They both can’t be right.

Liberal Democrat life peer Lord (Andrew) Phillips of Sudbury is upbeat. He would like nothing more than to see the Suffolk South constituency in which he lives fall to the Lib Dems, and belives Clegg can perform a national miracle.

Which makes this Thursday’s debate crucial. Cameron possibly has only one opportunity left to destroy Clegg. If he doesn’t, then the Tories could well see their election hope evaporate.