We would need four. I don't see that happening. Even if four seriously thought about, each would know that the pay back, from the other Democrats, would be a (expletive deleted). Even Jumpin' Jim Jeffords retired, after he handed the Democrats a majority, by switching parties, and Vermont lost some milk subsidies. Can you imagine the pay back the Democrats would extract? And if they ever got the majority back, any former Democrat, whose switch had cost them the Senate, would be a pariah, such as has not been seen since the Civil War.
No, any Senate Democrat, with a hope of a future career, won't switch, if it gives the Republicans control. And if they don't have hopes of a future career, why bother?
Webb, who was never able to give a succinct explanation of why he became a Democrat, may switch back. But he isn't running for re-election anyway.
Ben Nelson, who plays a moderate, when at home in Nebraska, might try to save himself, but I don't see him winning the Republican Primary. Mary Landrieu, who plays a moderate when at home in Louisiana, isn't up until 2014, but might switch early, especially given the weird "open" primary they have in Louisiana, but I don't see anyone else.
Thanks for your answer. You sure put some thought in it.
By the way, have you seen how they are reacting over at DemonUndgerground?
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=433x771914
I have even seen at least one of them demand that his/her account be deleted. They sure can’t take criticism.