He knows the people in CT have had it with him after the Countrywide kickbacks he took. He knows he would lose to a Republican in November. So by backing out now, he gives someone else a chance to hold the seat for the Democrats.
If Dodd wants to hold the seat for a demrat he needs to simply finish out his term. I did not see where he said he was retiring now or anytime before his term ends.
If he should retire early, and the governor appoints a demrat place holder, it would give that person a chance to win over the voters. So I guess that makes some sense. On the other hand, the way Onada and the demrats are going full speed ahead downhill, one wonders if demrat candidates as a whole will not be caught in voter crossfire.
I may be precipitous, but I think these demrat retirements/resignations indicate Onada does not have the votes for Onadacare.