Obamacare could still potentially be a positive for many Dems. "The reason why is easier to understand if you flip the issue around and look at it from the Republican side. Conservative orthodoxy still holds that Obamacare is a socialist abomination, and this requires Republican candidates to continue to advocate its repeal. It's true that the law's repeal is a strong motivator for Republican voters, and that does carry electoral advantages. But in practice, repealing Obamacare would entail dissolving popular state plans such as Kynect. Voters are bound to notice and make the connection."
Joshua Green in Bloomberg Businessweek.