IT'S the economy, stupid. So went the phrase pinned to Bill Clinton's desk by one of his aides during the 1992 US presidential election campaign. Its point was to remind Mr Clinton's campaign team that proving you can run a stable and successful economy is the key to political victory.

And it was ever thus. People vote with their pockets because they want governments that will make them richer. That is why the government acted so quickly in the wake of the Northern Rock crisis - and it is why the bank's customers voted with their pockets by queueing up to withdraw their cash.

The promise from the Government to guarantee the savings of Northern Rock customers had its desired effect yesterday as queues outside the bank's branches began to subside.

The challenge from today for the Prime Minister and the Chancellor is to ensure that the current volatility in the financial markets - which has its roots in the US mortgage market - has a minimal negative impact here.

Gordon Brown's political reputation has been built upon his handling of the economy during his time at the Treasury. He will not want to see that reputation battered on the rocks of an international financial crisis.

Mr Brown and Alistair Darling have a tough job ahead of them. Protecting the UK from the vagaries of the international money markets is hugely difficult. Completing the job successfully, however, could well be the defining moment for a Brown government still in its infancy.