Republican presidential contender Michele Bachmann, whose gaffes have made her a favorite punching bag for Jay Leno and other late-night comedians, paid Leno a visit Friday. In her first appearance on "The Tonight Show," Bachmann tried to show her lighter side — even making a joke about Christian anti-gay therapy, but Leno challenged her on gay rights, the HPV vaccine, her opposition to raising the federal debt ceiling and other conservative positions.