ABC News’ Rick Klein reports: One of Sen. John McCain’s most visible surrogates is scheduled to speak before an organization founded and led by Pastor John Hagee Tuesday night in Washington, despite McCain’s rejection of the endorsement by the controversial pastor. Sen. Joe Lieberman, I-Conn., is the keynote speaker at the Christians United for Israel Washington-Israel summit, where he’ll take the stage right before Hagee Tuesday evening, according to the summit itinerary. Lieberman, an Orthodox Jew, is one of McCain’s highest-profile supporters, appearing regularly alongside McCain at events and popping up frequently as a campaign surrogate. He is chairman of Citizens for McCain, a group for independents and Democrats who support McCain. He is widely discussed as a possible Republican National Convention speaker, and even as a potential running mate for the Arizona Republican. A McCain campaign spokesman said Lieberman is not going as an official representative of the campaign, and is free to do as he wishes in his capacity as a senator and advocate for Israel. “Sen. Lieberman is free to do what he wants and his support for Hagee’s work on behalf of Israel is well documented,” a McCain aide said. McCain rejected Hagee’s endorsement in May, after a tape emerged where Hagee suggested the Holocaust was caused by God to foster the creation of the state of Israel. Hagee, founder and senior pastor of Cornerstone Church in San Antonio, Texas, founded Christians United for Israel in 2006. Lieberman spokeswoman Erika Masonhall pointed out that the Connecticut senator addressed the same group last year — before he signed on with the McCain campaign. "[The appearance] his really has nothing to do with Sen. McCain," Masonhall said. "[Lieberman has] made it clear that he found some of Pastor Hagee’s comments in the past offensive, but he believes that the members of this group are patriotic Americans who are concerned about the war on terror." ABC’s Z. Byron Wolf contributed to this report.