Here are the remaining Democratic Senators who don't support
Heidtikamp, Donnelly, and Manchin strike me as pretty right wing.
Pryor and Landrieu are also pretty conservative and not from friendly states.
Johnson is retiring so might come out for it.
Bill Nelson tomorrow?
Pryor and Manchin seem to legitimately against SSM.
Johnson might announce support, but doesn't seem particularly supportive in the first place, nor does he want to hurt his son's chances if he runs.
Heitkamp has remained rather mum over the issue. Others have noted that she would support it if she wasn't North Dakota's senator. I agree.
Donnelly has always been fairly centrist, though I could see him supporting before the others, as Indiana is less socially conservative than the above states.
Landrieu won't support it yet, if she wants to win re-election. I think most democratics are okay with that. Her statements sound like she very much personally supports SSM, though. On a side note, I'm really beginning to appreciate Landrieu.
I think of all the D senators left, Nelson seems to be the only one who could conceivably support SSM without major negative ramifications. It would not be a complete surprise if either one of these three (in addition to Nelson) decide to announce their support: Heitkamp, Donnelly, or Johnson (and that's simply because he's retiring).
