[SmokingJoe]

“any Democrats considered too “damaged” to re-elect — and replace them with “more likeable” (and thus more electable) Democrats, in the hopes of maintaining a majority.”

Not gonna work.
Why?
Look at the Virgina governorship elections,
The Democrats had a new “fresh face” candidate (not the old incumnbebt governor), and they still got clobbered by a massive close to 20%, which is about the highest margin any Republican has ever won in statewide elections for decades.
It's not so much about individual Democratic Party candidates anymore, it’s the Tea Parties, It's the American voters being totally fed up with the Democrats(look at the latest Rasmussen generic congressional poll), and its about kicking the Democrats out of office.
All you need is to have a “D” after your name, and voters will vote against you.

[NewJerseyJoe]

I hope you're right -- but I disagree with you about Virginia. IIRC, even Democrats thought that Creigh Deeds was a loser candidate -- plus he'd been thrown under the bus by the Teleprompter.

The bottom line is that I won't trust a Democrat even one inch. I smell Pelosi and Rahm Emmanuel behind all (or most) of these resignations and droppings-out of races....