Paul Ryan factor fires up campaign

We'll see this week how Paul Ryan goes down in four key states, but he's already energised Mitt Romney.

The Republican presidential candidate beamed like a proud father as his pick for vice-president spoke to the crowd in Ashland, Virginia.

But it was when it his own turn to orate that the difference was really obvious. I have followed Mitt Romney around the primary trail, as well as on his less-than-well-received foreign tour. He's often competent, rarely inspired and always rather stiff.

But in this speech he seemed limber and loose, responding to the mood of the crowd and even rather enjoying himself. For once his performance was fierce and believable.

Making the candidate feel comfortable in front of a crowd is no mean service, but of course picking Paul Ryan is more important than that.

He is unknown to most Americans but has a high profile in Washington because of his radical plan to cut America's debt - that means he sharply divides opinions. Republicans (most, apparently not all) are delighted and feel Paul Ryan helps them argue they are a party of ideas and optimism.

But President Obama's supporters are already calling him an extremist ideologue who would hurt most Americans and help only billionaires.

Others argue his budget plan, widely praised as "serious", is in fact a piece of clever theatre that is poor economics.

Although it is fairly clear that both Democrats and Republicans in their own way will be "fired up" by the choice, it is as yet impossible to say how he will go down with swing voters and independents.

It could be that attention doesn't stay on the VP very long, but this does seem like a fresh phase in a campaign that had felt rather stuck in a rut.