Rat senators elected, if they take the senate, will indeed walk in lockstep with the left. Supposedly conservatives rats in the House will be a little more independent, but they will get hammered by Pelosi and the others until they're beaten down. Since rats don't have much in the way of principles anyway, they won't worry about it until it's time to run again.
That's the difference between the GOP and the Rats, the Rats know how to keep their guys in line, goes back to the LBJ days when he was Senate Majority Leader. We haven't had a Senate Majority Leader with any balls.