The political trio commemorated the 42nd anniversary of the 1965 civil rights march, paying homage to the heroes of "Bloody Sunday".
Obama, who hopes to become the first black president, said: "I stand on the shoulders of giants," to the ceremony at the AME church used as a headquarters by civil rights leader the Reverend Martin Luther King.
"I'm here because somebody marched for freedom."
Hillary Clinton, in a simultaneous speech at a Baptist church less than one street away, said that the voting rights won after the 1965 march had made possible her campaign to be the first woman president.
She also praised the march for allowing today's campaigns by Obama and Bill Richardson, the New Mexico governor, who would be the first Hispanic president.
Clinton said: "I know where my chance came from, and I am grateful. The people of
Both services ended with the candidates linking arms with other speakers and joining the audience in singing the civil rights anthem We Shall Overcome.
The two candidates later joined Bill Clinton and thousands of others in walking across the
The first woman president? [AFP]
In 1965, state troops violently attacked black marchers in a confrontation at the bridge that drew national attention and helped lead to the passing of voting rights legislation.
Hillary Clinton and Obama are the primary contenders for the 2008 Democratic presidential nomination.
Obama had been scheduled to give the keynote address at
Both candidates said the march should be seen as a beginning and urged a new generation to pick up the torch.
They praised each other at a rally outside the AME church before the march stepped off.
Clinton said: "I think it is so exciting that we have a candidate for president like Barack Obama who embodies all that was done right here 42 years ago."
Obama said he was glad
In praise of Bill
Bill Clinton was inducted in the
The first black president? [AFP]
"All the good speeches have been done today by Hillary and Senator Obama - I'm just bringing up the rear," he said.
Hillary Clinton, a
But recent polls have shown Obama edging closer to