Readers following Brian’s excellent coverage will have noted that Joe Lieberman rejected most of the amendments offered by Bernie Sanders to the Lieberman-Warner climate bill.

And if you watched the hearing, you’ll have seen that Lieberman was fairly obsequious to the Republicans on the subcommittee but briskly dismissive of Sanders.

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There are two theories for why this happens:

  • Ex-Dem Lieberman is congenitally deferential to those on his right and scornful to those on his left. It’s just an ingrained habit. He gave a tiny bit of ground to greens in private before introducing the bill, but in public? No.
  • Lieberman simply has nothing to fear from Sanders, because Sanders is not speaking for an active, powerful coalition. Boxer seems to have hung him out to dry, and the messages from the green community are mixed at best. Sanders is battling to push this bill farther as an individual, so Lieberman sees no reason to give him anything.

So which is it? Or have I missed a third option?

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