Senator Joseph Lieberman campaigned with Republican John McCain in 2008 (and was said to be McCain's first choice for Vice President). Lieberman was a headliner at right-wing religious extremist Rev. John Hagee's 2008 Christians United for Israel summit. (For Glen Greenwald's 2007 critique of the Lieberman-Hagee relationship, click here.) And this month, Lieberman threatened to vote against the Democrat's health care legislation if it contained a Medicare buy-in for those over 55-64 (something he was advocating last September). We talk with investigative journalist Ari Berman about what's behind Lieberman's bizarre behavior and what, if anything, the Democrats can do about him.