That isexactly what happened in Arkansas when Mark Pryor was elected to the US Senate a few years back - he ran as a conservative, family-values, outdoorsman, 2nd Amendment supporter. Of course, it took him exactly 1 day after moving into his office to join lockstep (99%+) with the liberal Dem Leadership. I forsee the same happening with all these Freshment Reps and Senators....regardless of if the Repubs hold onto the leadership in either house...
Congressmen have no such leeway. They are essentially locked into a permanent campaign cycle for reelection. Freshman congressman are the most vulnerable to getting turned out after only two years. These freshman Democrats will be very cautious their first term.