What on Earth Is Ezra Klein Talking about?

The Washington Post's Ezra Klein writes:

It's put-up-or-shut-up time for Republicans. They managed to make it through the health-care debate without offering serious solutions of their own, and - perhaps more impressive - through the election by promising to tell us their solutions after they'd won. But the jig is up. They need a health-care plan - and quickly.

The GOP knew this day would come.

Say what?  Exactly what political factors are forcing the GOP to put up or shut up?  Their base is happy; it wants an all-out assault on ObamaCare, and congressional Republicans are giving it to them.  Republicans are even winning the ObamaCare debate among the broader public:

So why should Republicans all of a sudden stop attacking ObamaCare and start talking about their own refor--ohhhh...I see.  Klein is trying to talk the dog off the meat wagon.  Good luck with that.