AKA the ruin-the-economy candidate.
Human progress since the Industrial Revolution has been based on cheap energy. While in principle I'm all for clean energy, on the timeline he's talking about it will result in a massive increase in energy costs, essentially running us backwards. (It does create jobs, but only in the broken windows sense)
He needs to find a position that's still progressive, but realistic. Voters, even the ones that are actually well-informed and think this through, are not going to pick a candidate that puts clean energy over the economy and their individual well-being.