I can't see why Lieberman should feel obliged to support a party that already kicked him out?
What I can't see is why Lieberman still persists in calling himself an "independent Democrat" when he clearly wants nothing to do with his old party.
Why did Zell Miller refuse to join the Republican Party? The only way he got any media attention was by technically remaining a Democrat.
I liken it to retired Bishop John Spong in my denomination. Bp. Spong rejects the basic teachings in the Nicene and Apostle's Creeds. But he refuses to leave the Episcopal Church, even though we pledge fealty to these beliefs daily, or weekly. Spong would fit perfectly in the Unitarian-Universalist tradition. And UU people are fine, wonderful folks! But why won't he leave our denomination, even though he doesn't believe the historic creeds?
Because the only way he can sell books and get interviewed is by remaining Christian, and rejecting basic Christian doctrine. If he were Unitarian, he would just be another Unitarian. If Zell Miller or Joe Lieberman were Republican, who would pay any attention to them?