I think he believes there's not a chance of it being included, and he's saying it to maintain his cred with the working class and to appear "fair and balanced".
Wow. I figured he was talking about some mythical trigger for a public option that would be impossible to reach, or that "cobble together" sounds like he's talking about state-by-state co-ops, but whatever, this can only be good for the passage of meaningful reform. Pet theory: he realizes he can't outcrazy Fox's new It Girl Glenn Beck by attacking from the right, so he plays up his self-perceived moderate centrism to hold onto relevance. Whatever the reason, even if he thinks the possibility is dead (and I doubt he'd support public option passage by reconciliation with 51 votes, which seems the only way), it's still good to hear.