Former US President Bill Clinton has fired up Democratic activists with a blistering attack on President George W Bush and fervent praise for John Kerry.
Clinton was introduced to the delegates by his wife, Hillary
Mr Clinton was speaking at the Democrats' convention in Boston which later this week will endorse Mr Kerry as the party's presidential candidate.
Mr Clinton accused Mr Bush and the Republicans of throwing away the goodwill towards the US after 9/11.
And he portrayed Mr Kerry as a Vietnam hero, ready to be a wartime leader.
Voters faced a stark choice in the 2 November election, Mr Clinton said, "between two strong men who love their country but who have very different world views."
The Democrats' nominee, John Kerry, favours shared responsibility, shared opportunity and more global co-operation, he said.
The Republicans and President George W Bush favour concentrated wealth and power, more unilateral action, pursuing a vision that is "far to the right of most Americans."
Kerry (r) picked running mate John Edwards earlier this month
On the eve of the gathering, polls suggested that Mr Kerry and Mr Bush are still running neck and neck.
In keeping with US political tradition, President Bush kept a low profile as the Democrats began their convention. But the Republican Party machinery continued working flat out to try to counter their opponents' message.
Mr Clinton - the keynote speaker on the opening night - was introduced by his wife, New York Senator Hillary Clinton, who called Mr Kerry "a serious man for a serious job".
Keen to draw attention to Mr Kerry's record of military service, Mr Clinton said many young men, including himself, President Bush and Vice President Dick Cheney avoided fighting in the Vietnam War.
"[John Kerry] could have avoided going too, but instead he said 'send me'".
Mr Clinton also launched into a detailed list of Republican failures, accusing them and President Bush of squandering the goodwill towards America in the wake of the 11 September attacks.
"They chose that moment of unity to try to push the country too far to the right, and to walk away from our allies."
They had attacked Iraq before the weapons inspectors had finished their work, withdrawn US support for the climate change treaty, for the international court on war criminals, for the anti-ballistic missiles treaty, and from the nuclear test ban treaty, Mr Clinton said.
"Now at a time when we are trying to get other people to give up biological and chemical weapons, they are trying to develop two nuclear weapons which they say we might use first. "
Earlier, another former President Jimmy Carter said: "Unilateral acts... have isolated the US from the very nations we need to join us in combating terrorism".
"You can't be a war president one day and claim to be a peace president the next," he said.
Al Gore, who narrowly lost the 2000 election to George W Bush called for "new leadership that will make us stronger at home and respected in the world".
He paid tribute to John Kerry's "deep patriotism that goes far beyond words".
"He showed uncommon heroism on the battlefield in Vietnam," said Mr Gore.
Shadow of terrorism
Security is tight at the event, which brings together 5,000 delegates, 15,000 guests and 15,000 journalists, amid concern that al-Qaeda may be planning another massive attack inside the US to disrupt the elections.
There are extra air, land and sea patrols and about 40 miles (65km) of roads have been closed.
More than 100 figures are expected to speak at the convention which runs until Thursday when John Kerry will address the delegates and accept the party's nomination.
The BBC's Justin Webb in Boston says no room has been left for dissent - and all the speeches must first be vetted by the Kerry team.