Treasury officials indicate it will take weeks, not months, to get the programme up and running – with Mr Paulson expected to spend about $50bn a month to buy troubled assets on behalf of the Treasury. But otherwise little is known about how the former Goldman Sachs chief executive would go about spending tens of billions of dollars to stabilise the financial markets.

The other imponderable is how the programme will affect whatever else the next administration plans to do. With just weeks to go before the presidential election, Barack Obama and John McCain, the Democratic and Republican nominees, have been loath to admit any impact on their ambitious plans, which range from promising billions of dollars in tax cuts to a national healthcare plan.

In the minutes before the House held its second vote on the measure, Nancy Pelosi, the Democratic House speaker, voiced the overriding question she still had about the legislation: “What does it do to our opportunities to invest in the American people?” She acknowledged that the next president and Congress, which is expected to remain in Democratic hands, would have to grapple with that query while keeping a close eye on the nation's ballooning deficit.