Charlie Crist and Artur Davis belong to the 2012 class of convention renegades -- politicians who have spurned their former political parties to appear at rival nominating conventions.

Crist, the one-time Republican governor of Florida who left the party to wage an independent Senate bid in the Spring of 2010, endorsed President Obama's candidacy on Sunday and will speak at the Democratic National Convention in Charlotte next week. Davis, a Democrat-turned-Republican former congressman who officially seconded Obama's nomination in 2008, is scheduled to speak in support of the president's GOP opponent in Tampa this week.

Crist and Davis each stand out this year. But this isn't the first time a high-profile pol has disavowed his or her former affiliation on the national convention stage. Here's a look back through history at a handful of memorable defectors:

* Joesph Lieberman, 2008: Declaring "country matters more than party," Lieberman, who eight years prior was the Democratic vice presidential nominee, delivered a defense of Arizona Sen. John McCain's record at the GOP convention in St. Paul, Minn. Lieberman, a longtime friend of McCain's and a senator from Connecticut lost in the Democratic Senate primary two years prior, but won reelection as an independent in the general election.

* Jim Leach, 2008: The Iowa Republican and former congressman's surprise endorsement of Obama and ensuing Democratic National Convention speech did not grab the attention Lieberman's appearance in St. Paul did. But he sounded a bipartisan note, which at many political conventions, tends to be in short supply.

* Zell Miller, 2004: Twelve years after he was the keynote speaker at Bill Clinton's 1992 nominating convention, the fiery Georgia Democratic senator and former governor delivered a keynote address at the convention where George W. Bush was nominated for a second term. In an animated address that didn't sit well with Democrats (and even some Republicans), Miller declared, “No pair has been more wrong, more loudly, more often, than the two senators from Massachusetts, Ted Kennedy and John Kerry. Together, Kennedy and Kerry have opposed the very weapons system that won the Cold War and that is now winning the war on terror.”

* Sarah/Jim Brady, 1996: Joined by her husband Jim Brady, the former White House press secretary to Ronald Reagan who was disabled in 1981 assassination attempt against the president, Sarah Brady, a Republican gun control advocate thanked President Clinton for signing the bill named after her husband. "Jim, we must have made a wrong turn. This isn't San Diego," Sarah Brady joked at the top of her Democratic National Convention address in Chicago. Republicans convened in San Diego that year.

* Jeane Kirkpatrick, 1984: Kirkpatrick was the first woman to serve as U.S. ambassador to the United Nations and was the only woman and only Democrat in Ronald Reagan's National Security Council. She spoke at the 1984 Republican National Convention where Reagan was nominated for a second term, dubbing Democrats "the blame America first crowd."