(CNN) On the 54th anniversary of a famous civil rights demonstration in Selma, Alabama, several Democratic presidential contenders joined Hillary Clinton in saying that not enough progress has been made to end voting discrimination and racism.

"The dream is under attack. The dream is in danger," said Democratic presidential hopeful and New Jersey Sen. Cory Booker.

Speaking in the historic Brown Chapel AME Church, where civil rights activists once assembled before their march over the Edmund Pettus Bridge, Booker said, "We have become a nation that is too adjusted to injustice, too content with the suffering of our neighbors, a nation that is too divided against ourselves."

On March 7, 1965, the day known as "Bloody Sunday," peaceful demonstrators demanding voting rights for black people were met by violence from police. Seventeen people were injured, including future Democratic Rep. John Lewis. The incident helped pushed support for the Voting Rights Act, which passed later that year.

"It's time for us to defend the dream," Booker said. "We must dream bigger dreams again in America that we can banish bigotry and heal hate and that we will elect leaders that know the only way to unite people. That is what it takes to make America great."

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