4 February 2013 Last updated at 06:53 ET

Article written by James Landale Deputy political editor

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Huhne triggers coalition by-election battle

But for a few votes in 2007, Chris Huhne could have been deputy prime minister today. Instead, his decision to plead guilty to perverting the course of justice means his career in politics is now over.

He will almost certainly face some kind of jail sentence. He has announced he will resign from parliament.

A by-election in his Eastleigh constituency in Hampshire will plunge the coalition parties into their first divisive contest in a very marginal seat.

Mr Huhne's majority there is just 3,864. Eastleigh is on the Conservatives' target list for the general election and David Cameron could use this as an opportunity to silence the doubters in his own party.

There would be nothing like a victory over the Lib Dems to answer the critics on his own backbenches. After the Lib Dems' refusal to back boundary changes that would have helped the Tories, their blood is up for revenge.

But if the UKIP leader, Nigel Farage, chose to stand in Eastleigh, he might divide the conservative-minded vote and allow the Lib Dems to hold onto the seat. Mr Farage did stand for the Eastleigh by-election in 1994 so he knows the turf. Today he said he'd think about it.

As for the Lib Dems, this is a huge blow. They have lost one of their big beasts who took the fight to the Tories.