Since Newt Gingrich's unlikely and sudden rise to the top of the Republican pack, the Obama campaign's smartest brains will have been doing a lot of brainstorming sessions. Until recently they would have been fairly confident that their opponent would be a methodical, cool-headed technocrat with an authenticity problem. They are now preparing for the possibility of facing somebody very different indeed.
The best presidential campaigns lock on to a weakness of their opponent and hammer at it ruthlessly and relentlessly. There can be sub-plots and variations but the core theme remains the same. The two major conditions for picking this theme are that (a) It provides a contrast with their candidate, and (b) It is rooted in truth.
In the most impressive re-election campaign of modern times, Bush overcame an unpopular war and a slowing economy by painting Kerry as weak and himself as strong, at at time when the country was fighting a "war on terror". Obama beat Clinton in 2008 by identifying her as the embodiment of old politics and himself as representing something new. In both cases, the contrast was rooted in truth: Kerry was prone to vacillation, and the Bush campaign cleverly made a virtue out of their candidate's stubbornness. Clinton, cautious by nature, had been around too long and done too much not to have made a long list of unpopular compromises (including her vote for the Iraq war) which allowed the Obama campaign to make a virtue out of their own candidate's inexperience.
If Obama goes up against Romney, the strategy, which the DNC is already laying down, is clear: Romney is a flip-flopper who doesn't know what he thinks. Obama knows his mind, even if you don't agree with him. In other words, a kind of economy-focused re-run of Bush vs Kerry.
The strength of this strategy is that Romney really does change his mind on everything and finds it hard, as a person, to convey authenticity. Its weakness is that the contrast isn't strong. Obama isn't Bush-like in his single-mindedness. His problem is that he can seem weak and ineffectual, and that is how Romney would seek to portray him. This would be a finely balanced contest.
How would Obama run against Newt? Ah, so many choices. They could portray him as an extremist. If he wins the nomination it will be because he's the hero of the conservative grass-roots. That will push him into taking up extreme positions (indeed he's already done so) and it will also bring him a lot of nutty followers. It may be difficult for him to tack back to the centre, where most elections are won.
They could paint him as the ultimate Washington insider - somebody who has spent the best part of his long life in that city, and who has made a fortune from lobbying.
Both these themes will get some play. But they will be sub-plots. The main story, I suspect, will be one of temperament. The Obama campaign, in a million subtle and unsubtle ways, will paint Gingrich as a volatile, unstable, deeply eccentric character who represents a real risk of calamity, at a time when the nation is already struggling to get out of its economic doldrums. As even conservatives agree, there's a lot of truth in that. It also plays to a genuine strength of Obama: his cool head, his reassuring predictability, his steadiness.
The Republicans nominated a fiery character last time, and that didn't go so well. Gingrich makes John McCain seem like George Bush Snr. If Newt is the nominee, 2012 will look like 2008, but more so.