The first time I heard astroturf used in a context other than sports fields was when the Tea Party movement started. We called it a “grass roots” movement — which it was. Then some jerk like Maxine or Pelosi tried to demean it by calling it “astroturf”. (Aren’t they just so SO clever? Blecccch!)
"Grass roots" is a term that's been around for a long time.
If Pelosi was accusing the Tea Party of being "astroturf," it's because history has shown us that Democrats always accuse Republicans of doing what they have been doing all along.
She called the Tea Party "astroturf" because it was probably a term they were using already to describe their own strategies.
-PJ