What's driving the stock bubble

I look at deficit/gdp (red), one year treasury rate (grey), ten year treasury rate(orange), and the SP500 bubble (purple). Real gdp is blue.

It look likes the fed holds one year rates low so government can raise deficit/gdp and that drives the bubble. And it seems we hit the bubble constraint a lot sooner than Delong would suggest. His claim is that we should hit an inflation constraint first, in the CPI or deflator. Instead the inflation constraint is in the stock market, it reaches peak bubble.
If we listen to Brad we will pump the bubble to infinity while Brad waits for consumer inflation to hit.