re: Chances of 19 Dems not toeing the party line?

Democrats flipping and voting no would be the smartest thing they could do in the long run. Yes, there would be some blowback from current Democrat house members but when election time came they would have a credible platform to stand on and drastically improve their chances for reelection. Doubtful any of them have the heart or balls to ride it out to completion though and the strategy only works if enough flip to kill the impeachment in the house. Any flips with continued impeachment proceeding makes the no vote look calculated.