The collapsing financial system and the public's response to last week's presidential debate yesterday propelled Barack Obama into his broadest opinion poll lead over John McCain since the Democratic convention in late August.

Polls released yesterday showed that Mr Obama, whose campaign is aggressively targeting formerly Republican states such as North Carolina and Virginia, has also taken a strong lead over Mr McCain in the important swing states of Ohio and Florida, which have tipped the outcome of previous contests.

According to a Quinnipiac University poll, Mr Obama leads Mr McCain by 51 per cent to 43 per cent in Florida, 50-42 in Ohio and 54-39 in Pennsylvania. Prior to last Friday's debate, in which, most observers agreed, Mr Obama's performance made him look more presidential, the two were running much closer.