I guess for a lot of them Blue Dog Democrat means

"Kick me and pee on me, but if you scratch my ears enough to stay in office I'll pee all over the people back home for you."
Pelosi cut deal after deal with individual lawmakers to squeak the bill out of committee and to the floor. Then lawmakers flew home and had to battle criticism from voters at the same time Republicans were saying Democrats passed an “energy tax.”

“They went home and got beat up about energy,” said a senior aide to a Blue Dog lawmaker. “Now you’re going to jam healthcare down their throat and send them home for a month?”

One of the goals of having the seven Blue Dog members band together is to guard against leadership picking centrists off one by one with side deals, as they feel was done during the energy vote.
Translation: "We'll do what you want, but if you do it this way we have to listen to the hicks back home yell at us, and we don't like that."
But defections could be hard for Republicans to come by. As difficult as the climate change vote was, Republicans were unsuccessful in getting enough Democrats to block the bill.

And what many Republicans oppose outright, Democratic centrists oppose in degree. For example, Republicans object to a government-run “public option.” Many Blue Dogs have come to accept that it will be part of the bill, but don’t want it to use reimbursement rates from Medicare that they believe shortchange their rural areas.
"We won't stop the bill, but we want you to buy us off properly, dammit!" They know what a mess this garbage is, but they won't stand against it; they'll stand against enough to get their ears scratched, and then roll over.