ABC News’ Teddy Davis reports: Former top McCain adviser Steve Schmidt is planning to use a Friday speech to the Log Cabin Republicans to urge the GOP to drop its opposition to same-sex marriage. "I’m confident American public opinion will continue to move on the question toward majority support, and sooner or later the Republican Party will catch up to it," Schmidt plans to say according to excerpts provided to ABC News. Schmidt’s push for Republicans to endorse same-sex marriage comes as his party is grappling with a string of gay rights victories in Iowa, Vermont, and Washington, D.C. Schmidt’s former boss, Arizona Sen. John McCain (R), continues to oppose same-sex marriage while also opposing a federal constitutional amendment prohibiting it. McCain’s daughter, however, has become an outspoken advocate of same-sex marriage recently and is slated to address the Log Cabin Republicans on Saturday evening. The topic of her address is: "Losing the Next Generation: How can the Republican Party Attract More Young Voters?" In his Friday noontime speech, Schmidt is planning to argue that same-sex marriage is in step with principles that conservatives hold dear. "There is a sound conservative argument to be made for same-sex marriage," Schmidt plans to say. "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." "It cannot be argued that marriage between people of the same sex is un American or threatens the rights of others," he will say. "On the contrary," he will say, "it seems to me that denying two consenting adults of the same sex the right to form a lawful union that is protected and respected by the state denies them two of the most basic natural rights affirmed in the preamble of our Declaration of Independence — liberty, and the pursuit of happiness. That, I believe, gives the argument of same sex marriage proponents its moral force." While seeking to appeal to conservative principles, Schmidt is also planning to make an electoral case for same-sex marriage. The former McCain adviser believes that Barack Obama’s large margin of support over McCain among voters under 30 was due, in part, to younger Americans being comfortable with giving gay couples equal rights under the law. "Some Republicans believe the period of self-examination within the party necessitated by the loss of our majority status is mostly a question of whether the party should become more moderate or conservative," Schmidt plans to say. "I think that’s a false choice. We need to grow our coalition, but as I said, that’s hard to do if we lose some votes while gaining others." Prior to leading McCain’s 2008 presidential campaign, Schmidt managed California Gov. Arnold Schwarzenegger’s (R) 2006 re-election campaign. He also served in the Bush White House where he played a leading role in the confirmations of Chief Justice John Roberts and Justice Samuel Alito to the Supreme Court. He is currently a partner with Mercury Public Affairs in Sacramento, Calif. He first endorsed same-sex marriage in an interview last month with the Washington Blade, a gay newspaper. Following Schmidt’s address to the Log Cabin Republicans, he is planning to take questions from convention attendees. He will then hold a media availability. The Log Cabin convention is taking place at the Westin City Center in Washington, D.C.