More importantly, there will be a mad dash to find someone to switch parties and shore up a majority. In 2000, that person was Vermont Republican Jim Jeffords. In 2008, Democrats convinced a beleaguered Arlen Specter to give them a true governing majority. And there were rumors in 2006 that, had he won re-election, Linc Chafee was prepared to make Harry Reid Majority Leader if need be.
With this in mind, here's a list of the top five potential Senate party switchers and a discussion of how likely each one is to switch:
#5. Mark Pryor – This Arkansas senator has to be looking at what is happening to the senior senator from his state with dread. After all, the question isn’t whether Blanche Lincoln is going to lose – it is by how much. Pryor’s voting record is actually the slightly more liberal of the two, and he’s going to have another two years of voting on the Democratic leaderships’ priorities if Schumer or Durbin is the leader.
But at the end of the day, it is hard to see this switch happening. Pryor is a scion of a prominent Democratic family in Arkansas, and he isn’t so far to the right that he’s completely out of place in the Democratic caucus. He’ll probably gut it out for four years and hope the environment improves. Chance of a switch: <1 percent.
#4. Joe Lieberman – Most readers will be shocked to see Lieberman this far down the list. After all, he endorsed John McCain, left the Democratic Party based on his support for the Iraq War, and torpedoed the “public option” in the health care bill. And as an independent, technically wouldn’t even have to switch parties – he’d just have to caucus with the Republicans.
But Lieberman could have switched parties in 2006 and handed control of the Senate back to the Republicans, but didn't. It probably would have made more sense back then when the Iraq War was a hotter issue. Lieberman’s apostasies tend to be on discrete issues – his overall voting record is just to the right of middle of the Democratic Party. At the end of the day, he really is a Democrat, and it is hard to see him feeling comfortable in a Southern-dominated Republican caucus. Chance of a switch: 1-2 percent.
#3. Jim Webb – Jim Webb is already a two-time party switcher. The former Reagan Administration official switched to the Republicans during the Vietnam War, and then switched back to the Democrats at some point in the 2000s. The biggest reason for his most recent turnabout, the Iraq War, has faded into the background of the national debate, and he actually may feel more at home with Republicans than Democrats on some issues.
But there are two reasons this probably won’t happen. First, Webb is really a man without a party. He’s a Jacksonian, and part of this is a strong streak of economic populism that is out of place with the modern GOP. Second, and more importantly, he’d have to make it through a GOP Convention to secure renomination, which seems almost impossible. It’s more likely he’ll hang up his spurs after one term. Chance of a switch: 2-3 percent.
#2. Ben Nelson – Nelson is without a doubt the most conservative Democrat in the chamber, and with good reason: He represents one of the most Republican states in the Union. On a wide swath of issues, from abortion, to taxation, to gun rights, he is already a far more certain vote for Republicans than Democrats.
There’s just one little thing. He already voted for the Democrats’ health bill, destroying his credibility with Republicans. If he were going to switch parties, it would have made sense during the Bush Administration, or during the health care debate. It’s almost certain that he’d get the “Specter treatment” in the 2012 Republican primary. He may choose to take his chances with the general electorate. More likely, the 69-year old Nelson will just retire. Chance of a switch: 5-10 percent.
#1. Olympia Snowe – For all the talk of a switch among Democrats, the most likely switch probably comes from the Republicans. Snowe had to be watching with horror as Arlen Specter left the party in advance of a surefire primary loss, and then fellow moderates Lisa Murkowski and Mike Castle lost Senate primaries to very conservative candidates. Her party has nominated a very conservative candidate for governor in two successive elections, as Maine moderate and liberal Republicans have switched their registration to Independent or Democrat.
She’s already cast a vote for a version of the health care bill, which makes her odds of surviving a primary challenge in 2012 fairly slim. But she also has to fear the “Specter treatment;” if she were going to make this move, it probably would have made more sense to make it in early 2009, giving her four years to build up her Democratic credentials. Chance of a switch: 15-20 percent.
http://www.realclearpolitics.com/articles/2010/11/01/what_happens_in_a_50-50_senate_107795.html