With the economy haemorrhaging jobs and little sign of victory in Iraq, the CNN/USA Today poll gave Mr Bush an overall approval rating of 52%, compared with 55% in an ABC/Washington Post poll taken between September 6 and 9 2001.

His continuing downward trend in the polls suggests that the weekend's televised address to the nation, in which he asked for $87bn for the war in Iraq, did nothing to reassure the electorate and may even have made things worse.

This summer has seen a steep decline in the president's standing from a high of 71% approval in April, suggesting that he would face an extremely close battle if there were an election today. Asked whether they would vote for Bush or an unnamed Democrat, the president has only a four-point lead; in August it was 12.

Support for and opposition to Bush is deeply partisan, reflecting growing entrenchment among Democrats and Republicans. But of particular concern for the Bush teams, according to other polls, is the low number of independent voters (33%) who approve of the overall job he is doing.

"Taking a fall was inevitable, but he is increasingly vulnerable now," Jaime Regalado, a political scientist at California State University, told USA Today. "The war in Iraq is showing escalating costs in money and human life and the American public is showing escalating doubts."

In the latest poll 58% say "the situation in Iraq was worth going to war over", down from 63% in August. More than half think things are going moderately or very badly in Iraq, while 59% believe the administration does not have a clear plan for handling the situation there.