Sanders not voting for bill unless it improves

Via ThinkProgress, here's Sen. Bernie Sanders (I-VT) interviewed by Neil Cavuto earlier today:

As of this point, I’m not voting for the bill. ... I’m going to do my best to make this bill a better bill, a bill that I can vote for, but I’ve indicated both to the White House and the Democratic leadership that my vote is not secure at this point. And here is the reason. When the public option was withdrawn, because of Lieberman’s action, what I worry about is how do you control escalating health care costs?

This is a big deal. Bernie Sanders has got to be facing incredible pressure, the likes of which Joe Lieberman or Ben Nelson have never seen. If he manages to hold firm to his position and improve this bill, he'll have shown that you can't always count on the left to cave to the right. That would be huge.