The Carpetbagger Report has a neat nutshell analysis of the precarious balance that keeps Joe Lieberman in the Democratic caucus, even though he isn't a Democrat any more. He lost the Democratic nomination last cycle to a great newcomer (Ned Lamont), split Connecticut's Democratic vote by running as an Independent, is endorsing and campaigning with John McCain, was considered as Don Rumsfeld's replacement for Bush's Secretary of Defense, had his superdelegate credentials pulled by the Connecticut Democratic Party, and may be giving the keynote speech at the Republican National Convention. Why haven't the Democrats booted him? Because right now the balance between Democrats and Republicans in the Senate is exactly even, and if Lieberman ditched the Democratic Party then Dick Cheney would effectively become Majority Leader. Which, of course, would be a very bad thing.
All the above is a mess, but things may get even more complicated as we approach the two national Conventions and the general election. A win by either of the Democrats could have "coattails" that also helps downticket candidates for the House and Senate. Obama, in particular, is very likely to help Democrats add a couple more Senate seats, because his strategy in both the primaries and the general election is to win more, if smaller, states while Clinton is aiming at the larger, voter-rich states. (Those two approaches -- more states with fewer voters versus fewer states with more voters -- add up to be roughly equivalent in terms of total electoral college votes for President, but since small states and large states alike have the same number of Senators -- two -- the candidate who wins hearts and minds in a greater number of states, regardless of size, will give coattails to more of his party's Senate candidates, as well. Incidentally, this is another reason I don't think the Superdelegates will override the popular vote and hand the Dem nomination to Hillary, but that's another post.)
If the Dems can gain just one more seat next November, then they don't need Lieberman to retain a majority any longer; he'd lose his ability to blackmail them with the threat of a Cheney-dominated Senate, and Lieberman would lose both his remaining political pull and his committee chairmanship. Hopefully he'd retire at the end of his term, leaving the path open for Ned Lamont to take his rightful seat.
The problem is that Lieberman knows this math better than anyone -- and he's self-centered and manipulative enough to take steps to secure his power. How? By making sure that the Democrats don't win in November. And what's the most helpful thing he could offer the Republicans? It's obvious: for Al Gore's vice-presidential running mate from 2000 to announce that his beloved Democratic Party has abandoned common sense and is weak on defense and hates Israel and loves terrorists yadda yadda -- then cap his betrayal by giving the Republican National Convention's keynote address.
---EOE---
http://www.huffingtonpost.com/m.s.-bellows/the-new-zell-miller-the-d_b_97791.html