So far Hillary Clinton, Barack Obama and John Edwards have committed to participating. This is a groundbreaking event--never before have top-tier presidential candidates come together during a primary season to discuss LGBT issues.
Joe Solomonese (HRC's Exec. Director) and Melissa Etheridge will moderate/emcee the August 9 event, (a lesbian in our office wonders why the male is a political figure/advocate and the female is an entertainer...) which will be broadcast live on Logo from Los Angeles.
Republicans are also invited to participate.
Read the press release here (via Queerty)