Vice-presidential debates can be a springboard to the top job in the US.

And now to the veeps, one actual, one would-be.

On Friday, Paul Ryan and Joe Biden face off for their single vice-presidential debate, and it should be fun.

Both are engaging characters; both enjoy a joke. Biden has an endearing habit of putting his foot in his mouth. Ryan is prone to statistical whoppers as he pursues the partisan fight, but his choirboy looks and disarmingly friendly style make it easy to forgive him. But what makes their confrontation especially interesting is that, suddenly, the stakes are higher.

Normally, vice-presidential debates are part of the campaign undercard. Yes, they've produced the odd great line - none better than Lloyd Bentsen's withering "senator, you're no Jack Kennedy" put-down of Dan Quayle in 1988, which actually had you feeling sorry for Quayle. Bentsen won at a canter, but his debating skills didn't prevent Michael Dukakis from being soundly beaten by George H.W. Bush in the election.


But President Barack Obama's dismal performance in his first debate with Mitt Romney, just when it seemed he was cruising to re-election, may have changed the trajectory of this race. The supposedly hopeless Romney showed he wasn't so hopeless after all, and Republicans who had virtually given up on their man are now galvanised, with a genuine belief that he can win.

I went down in Fisherville, real God-and-guns country in deepest Republican Virginia, to attend Romney's first post-debate rally. The atmosphere was positively festive, transformed by their man's blowout win over Obama. The grassroots activists will now be more active on behalf of the cause than ever, and big party donors, who might have found better things to do than bankroll a loser, will keep the money flowing in.

The President did catch a huge break the next day, with the news that the unemployment picture had improved in September, suggesting that his policies are working, albeit slowly. And not only the labour market figures: the most recent data for consumer confidence and the housing market, not to mention a gradual rise in stock prices, also point to an economy that is on the mend.

Best of all for Team Obama, the jobless rate fell to 7.8 per cent, the lowest since he took office. No longer will we professional sifters of tealeaves quite so often be reminding him that no incumbent since FDR has won a second term when the jobless rate is 8 per cent or more. Even so, the horse race is probably tightening, and Joe will have to be careful. A bad goof on Friday may not be as inconsequential as usual.

In one notable respect, however, the Ryan/Biden matchup does fit a familiar pattern, of the young pup against the grizzled veteran.

One thing, however, is certain. Ryan will be with us for a while. A couple of months ago, just after Ryan was chosen as Romney's running mate, Nate Silver made a statistical examination of his prospects, in his ever-informative FiveThirtyEight blog in the New York Times. It confirmed that the best shortcut to the Oval Office is via the vice-presidency. Mere nomination guarantees that priceless asset for the future: name recognition. Independent