Peter Beinart explains why.
It is the absence of such a worldview that allows Lamont to wax hawkish about North Korea while urging near-immediate withdrawal of troops from Iraq. And that allowed congressional Democrats to demagogue the Dubai ports deal, even as they criticized the Bush administration for alienating Arab public opinion. Lamont's critics are wrong: Ideologically, he is not Carl Maxey [challanged Scoop Jackson in 1970], and his supporters are not mostly McGovernites. The greater danger is that he is Jimmy Carter or Michael Dukakis, and his supporters are like the Democrats who wandered in the post-Vietnam, pre-Clinton intellectual wilderness: able to describe the conservative vision they abhor but not the liberal alternative they propose.