Having received little or no "bounce" in opinion polls from the start of the Democratic convention or his selection of running mate Senator Joe Biden, Mr Obama is set to tone down his lofty rhetoric and attempt to connect with ordinary Americans by focusing on how he will end their economic woes.  Advisers to the Illinois senator are nervous that the speech, which marks his official acceptance of the Democratic presidential nomination, will play into the hands of his Republican opponent John McCain, who has accused him of being a self-obsessed celebrity. Gallup's tracking poll had Mr McCain ahead by two percentage points on Tuesday and Mr Obama up by one on Monday.  Confusion has reigned over whether or not Mr Obama's appearance will be accompanied by various musical stars. It is now thought that while the crowd will be treated to performances by Stevie Wonder, Sheryl Crow and Will.i.am, whose video "Yes We Can" put music to Mr Obama's speeches, Bruce Springsteen will not appear. Party officials' nervousness over the issue has added to the sense that Mr Obama is keen not to be linked to celebrities.  Coming exactly 45 years after Martin Luther King's "I Have a Dream" address, Mr Obama's appearance is also set to evoke John F. Kennedy's convention speech in Los Angeles in 1960, the last time an acceptance was made outside the main hall. However, Mr Obama's advisers were keen to stress that he would be concentrating on policy detail.  A spokesman for Mr Obama said: "The hope is that after watching this speech people will know a little bit more about who Barack Obama is, where he comes from and where he wants to take this country."  The pressure to deliver heaped on Mr Obama, the first black nominee for the White House, by a rousing speech at the convention by Hillary Clinton, the former First Lady, whom he narrowly defeated in the primaries, was eased slightly by her husband Bill, the former president, who delivered a surprisingly whole-hearted endorsement.  In a solid public backing aimed at putting to rest the rift between the two party factions, Mr Clinton told delegates that Mr Obama is "ready to be president of the United States."  "Barack Obama is ready to lead America and restore American leadership in the world: ready to preserve, protect and defend the constitution of the United States," Mr Clinton said.  In a theatrical declaration of unity, Mrs Clinton later took to the convention floor, microphone in hand, to urge the party to abandon the roll call of states' nominations for the presidential candidacy and deliver it to Mr Obama.  "With eyes firmly fixed on the future, in the spirit of unity, with the goal of victory, with faith in our party and our country, let's declare together in one voice right here, right now, that Barack Obama is our candidate," she said.  In his own speech Senator Biden, with whom Mr Obama will embark on a tour of battlegrounds states on Friday, signalled the commencement of a more personal line of attack on Mr McCain, from which the party have so far held back.  Atempting to tie Mr McCain with the unpopular Bush administration, Mr Biden said Mr McCain would simply continue on America's present course in foreign and economic affairs. "John McCain was wrong. Barack Obama was right," on these and other issues, he said.  "Despite being complicit in this catastrophic foreign policy, John McCain says Barack Obama isn't ready to protect our national security," Mr Biden said. "Now, let me ask you, whose judgment should we trust? Should we trust John McCain?"
Barack Obama will stride out from beneath a mock Greek temple on a stage fit for a rock star to deliver a speech before 80,000 people to pave his way to the White House.