Debate - The Ed v Nicola Show

BBC debate Image copyright PA

Some thought David Cameron would pay a heavy price for not turning up for tonight's debate. Certainly there are voters who will be angry that the prime minister refused to take part in more than one debate.

Clearly he missed a chance to make the Tory case and left the stage free to his opponents. Finally, Ed Miliband was able to challenge his opponent to have the courage to debate with him head-to-head.

However, I suspect the prime minister will think that tonight went pretty much as he hoped it would.

Why? Because what will stick in the memory is not the man who wasn't there but the row that was.

Ed Miliband faced attacks from the SNP's Nicola Sturgeon backed by Plaid Cymru's Leanne Wood and the Greens' Natalie Bennett for being "Tory Lite", letting the Tories off the hook and not being bold enough.

This may allow the Labour leader to be seen as more moderate than his left wing rivals. There is, though, a big chance that this will simply boost Labour's rivals and split their vote.

Nicola Sturgeon showed once again what a formidable debater she is. She took every opportunity to stress that she wanted Labour in power, but only if it were more radical than it is now.

The video clips of those clashes are likely to be what gets played and replayed. That won't worry the Conservatives one jot as they are desperate to convince voters in England that they face the threat of weak Labour prime minister propped up by a strong SNP .

There's just one thing that may worry Tory HQ. Nigel Farage was left entirely free to appeal directly to right-leaning voters worried about the size of the deficit, defence spending and immigration.

This was a debate unlike any we've ever seen. I can't believe there will ever be another like it.

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