If history is any guide, the answer is: They will back whoever is most likely to win. But while this current situation has similarities to others in recent years, it brings with it some dynamics that we simply haven’t seen. There are two other independents who have caucused with the Democrats: Angus King of Maine and Bernie Sanders of Vermont. Both are more reliable votes for the blue side, and in large part because of that, neither has faced a Democratic challenger like Sinema. … Sinema is one of the two most unpopular members of the Democratic caucus in Washington. … And given the distaste for her from the ranks of activists and donors — combined with growing intolerance, from the grassroots of each party, of supposed renegades — it may be very difficult for national Democrats to support her, or even and disqualify the match. And that goes double considering Arizona is a swing state… The real problems creep in if it looks like Sinema has a better shot than the Democratic nominee, whether that’s Rep. Ruben Gallego (D-Ariz.) or someone else. At that point, the party will surely want to back the most likely winner, as it almost always does — and especially in a year in which the party is expected to play an extended defense while defending its narrow 51-49 majority. But selling that decision to a West Virginia Democratic base that feels like it should be a loyal party-line vote would be another matter entirely.
