Washington (CNN) - Steve Schmidt, a key architect of John McCain's presidential campaign, is making his first public return to Washington a bold one. Schmidt will use a speech Friday to Log Cabin Republicans, a gay rights group, to urge conservative Republicans to drop their opposition to same-sex marriage, CNN has learned. "There is a sound conservative argument to be made for same-sex marriage," Schmidt will say, according to speech excerpts obtained by CNN. "I believe conservatives, more than liberals, insist that rights come with responsibilities. No other exercise of one's liberty comes with greater responsibilities than marriage."