I suspect that Sarkozy will be the lesser problem: the mantra of work unites the son of the Manse with the son of Hungarian Jewish immigrants, both driven by an obsession with capturing the top job.
But Scotland is another matter. The problem will not be the guerrilla war Salmond will wage against the Trident nuclear submarine bases or his relentless criticism of the war in Iraq. The real crisis will come if attempts to buy off the call for independence - for example by ceding more power to the Scottish Parliament - provoke the slumbering, but increasingly twitching, giant of the Union that is England.
Brown knows this very well. His response to the challenge posed by Salmond has been to define an over-arching Britishness which is common to the Union's different nationalities. He defines this Britishness in terms of shared values.
I suspect that John Major's Betjemanesque image of cricket played on a village green against the backdrop of the church tower and warm beer being served in the tea tent gets closer to the mark. This is not because it is a typically British scene - indeed, it's a little nostalgic even as an English image - but it's because it gets us closer to the institutions and behaviour which more accurately define us. Shared experiences on the personal and popular level, history, a sense of place, high culture, popular culture, sport: these are the elements which stitch together the 'soft' fabric of the nation. The hard shell - defence, security, prosperity - are the responsibility of the nation incarnated as a state.
Add to this soft underbelly of culture the institutions which define our public processes, such as monarchy, Parliament, common law, the police and armed forces, civil society, and we are perhaps closing in on the things which make us feel at home.
But are these English rather than British? I suspect that to a significant extent they are. What resonance does the monarchy have in Scotland other, perhaps, than in the person of the Queen?
And is it not the case, perhaps, that south of the border all political parties are neo-Liberal and north they are all social-democratic? Would a Conservative general election victory in England sharpen the mood for independence in Scotland?
Which brings us back to the slumbering, twitching giant. Ceding more powers to the Scottish Parliament is pretty close to a zero-sum game for the English. How tolerant will the English be of Scottish MPs at Westminster if there are even fewer decisions to be taken there concerning Scotland and their voice in English matters consequently even more intrusive? Given that the Conservatives won the popular vote in England in 2005 and seem certain to score more heavily in that in 2009 or 2010, how tempted will they be to play the card of English votes for English laws?
I suspect this is the real threat to the Union. No party, so far as I am aware, has put forward a coherent shopping list of new powers for Edinburgh. But when and if they do so they must not assume it is just another shopping trip to the Westminster Tesco. The hurdles to independence are very considerable indeed but devolving more powers is not the easy way out.
Gordon Brown should make it a priority to burnish the machinery of inter-governmental relations in order to engage the Nationalists. Scottish Labour MPs in Westminster might start by sparing us the pathetic polemics about the Nationalists which simply feed the Nationalists' glee.
Scotland's fate will be decided in England - by the twitching giant.