The Nick vs Nigel sideshow

Finally, the recognition he has fought so long to achieve -- a place on the main stage, standing shoulder-to-shoulder with the big players.

Yes, Nick Clegg has finally earned a debate with Nigel Farage.

The BBC's confirmed it will broadcast their encounter, but also that it will be on BBC 2 -- it's important, but not so important that it's worth cancelling The One Show.

We could largely script this debate already -- Nick's for the EU, Nigel's against.

It's all a bit pointless without Dave and Ed. The Labour leader might just be thinking about joining in, if only to highlight the fact the Prime Minister is missing.

The last thing David Cameron wants to do is share a stage with Nigel Farage, a statement of parity he's desperate to avoid in the run-up to May's European elections.

At his spring conference last week, the UKIP leader raised the prospect of his party "winning" the Euro vote.

And that's a distinct possibility -- five years ago they came second to the Tories, with more than 16% of votes.

But in 2009, David Cameron was the opposition leader -- now he's Prime Minister -- his party no longer a home for protest votes, he's expecting a bad night.

But there's every possibility that, while UKIP will "win" the European election, they'll then achieve next to nothing at the general eleciton a year later.

It's almost impossible for UKIP to win a Westminster seat, unless they follow the Green strategy in 2010, and throw all their energy into a single contest -- that would be a big strategic change.

Instead, UKIP's chief victory will be to drag the Conservatives to the right, making the task of winning an outright majority even harder.

David Cameron's promise of an in/out referendum in 2017, and promises of tougher action on EU migration, are a direct consequence of the rise of UKIP.

It's grabbing traditional right-wing Tory voters who in the past had nowhere else to go, and pushing Mr Cameron further and further to the right, in an effort to shore up core voters -- a strategy which carries a huge risk.

No Conservative Prime Minister has increased his party's share of the vote since Sir Anthony Eden in 1955. Even Margaret Thatcher's 1983 landslide was on a smaller share than her first win four years earlier.

Elections are fought and lost on the middle ground -- and every UKIP defector persuaded to stick with the Tories may be cancelled out by the loss of more moderate Conservatives or Lib Dems uncomfortable with tougher, right-wing, rhetoric.

The core vote strategy hasn't worked too well for the Tories in the past. David Cameron helped to write the 2005 manifesto, dominated by immigration, welfare and Europe.

It got the grassroots Tories to the polling stations, but put some disgruntled Labour voters off a switch.

What would all this mean? If the Tories find themselves scrapping for right-wing votes, and end up neglecting floating middle ground voters, it could threaten the gains the party needs to govern alone after 2015.

That's good news for Ed Miliband. And it could be good for Nick Clegg too. Two-thirds of Lib Dem seats are held against Conservative opposition. A Tory vote split by UKIP could be enough for some of them to hold on.

Nick and Nigel will bicker in their hour in the BBC 2 spotlight -- but it could be a UKIP surge might be the best thing for both of them.