Senior Democrats on Monday kicked off the presidential convention admitting that Barack Obama’s campaign was going through a prolonged tough patch, following John McCain’s decision to sharpen his attacks on the Democratic candidate over the past few weeks.

Dick Durbin, Mr Obama’s fellow senator from Illinois and the man who introduced him to the nation at the last Democratic convention in Boston four years ago, said Mr Obama had been hurt by the Russian invasion of Georgia and his decision to take a week’s vacation in Hawaii earlier this month.