CHARLOTTE, N.C. (AP) - The Democratic National Convention's keynote speaker says middle-class families paid the price for failed economic policies that GOP presidential candidate Mitt Romney is proposing anew.

San Antonio Mayor Julian Castro says Republicans believe that if the most prosperous Americans do even better, than everyone else will, too. But Castro says that "trickle-down" theory of economics has been tried before and doesn't work.

According to excerpts from the speech Castro is delivering Tuesday night, he credits President Barack Obama with pulling the country back from the brink of a depression nearly four years ago and creating 4.5 million new jobs.

The 37-year-old Castro is a rising star in the Democratic Party. He is the first Latino to deliver the keynote address at a Democratic National Convention.