"You're going to see each of these new governors try to move his or her state into a leadership role, and that's a good thing," Learner said. "But you're also going to have to find common cause with Republican governors in Indiana, Ohio and Iowa."
There's also the challenge of working with or around the Trump administration, which has rescinded the Clean Power Plan and scrapped much of the framework that states were planning to use to make energy transitions over the next 50 years.
Rabe said he believes that in the absence of federal leadership, more states will begin looking at innovative ways to bring their carbon emissions down, including through market mechanisms.
"If the band is getting back together, it will be with an entirely new set of players," he said of MGGRA, "and they will probably be playing different music."