The way I see it, there is no option not to focus R&D on green energy and other related tech.
And you know, government does these things pretty well and generally comes out on top:
catalytic converter, seat belts (two necessary and roundly-accepted technologies that were, at the time--"the doom" of the industry if the car manufacturers had their way, complaining about how the imposed costs would bankrupt them).
Not focusing on something "until it is mature" is a good way to hope that it never matures. I don't like that.
I like NASA. I like space exploration, going to the moon. I like colliding Hadrons. This is what advanced economies should be doing. This is what makes humans awesome. And, quite frankly, we really do not have a choice. I wouldn't worry about anyone lighting a match to the existing fossil fuels and forcing our hand to turn green energy into the next NASA project--that's somewhat of a populist detraction, imo.
Hell, all we have to do is convince Congress that, as always, green energy innovation is the best path to shiny weapons and blowing shit up, and they'll just toss bags of money at it. Presto! Innovation. It's why we have NASA, why we have/had Fermi labs and almost had that massive accelerator in NM (blame the Russians for going non-commie for the loss of our accelerator.

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The Obama 50 mpg is hardly an overreach, and certainly will not fail. This marks the third (4th?) time that the gov't has mandated better efficiency in cars. Every time the makers bitch and moan about cost. Every time they convince some segment of the population that this will, indeed, doom the auto industry.
It never happens. Cars become more efficient. The makers make more money. Everyone is happy. It's one thing to make such a prediction, it's quite another to consider the long history of that very same prediction and continue to make the wrong prediction.