He’s not in favor of the public option at all:

“We’re trying to do too much at once,” Lieberman said. “To put this government-created insurance company on top of everything else is just asking for trouble for the taxpayers, for the premium payers and for the national debt. I don’t think we need it now.”
[…]
Lieberman said that he’d vote against a public option plan “even with an opt-out because it still creates a whole new government entitlement program for which taxpayers will be on the line.”
[…]
“I’ve told Sen. Reid that if the bill stays as it is now I will vote against cloture,” he said.
“I can’t see a way in which I could vote for cloture on any bill that contained a creation of a government-operated-run insurance company,” Lieberman added. “It’s just asking for trouble – in the end, the taxpayers are going to pay and probably all people who have health insurance are going to see their premiums go up because there’s going to be cost shifting as there has been for Medicare and Medicaid.”

Snowe doesn’t sound like she’ll support it either. Looking like they’ll have to drop it to get it out of the Senate.
BTW, no one is fooled by Reid’s attempt to make the public option more acceptable since we all know that only places like Texas have the votes to opt out of the plan. States like California, NY, and NJ would be stuck with it.
Update: The House doesn’t have enough for a “robust” public option.