The false radicalization

Gillian Tett is usually excellent, but here  she reproduces a false argument about recent polarization in the US (and some other parts of the world?).  According to her "On one side of the spectrum, Tea Party activists have been brandishing the constitution and declaring “no surrender” on fiscal issues, even at the risk of sparking an American default. On the other side, leftwing parts of the Democratic party have been equally intransigent."  

Where are those leftwing parts of the Democratic party?  How much power do they have?  Is defending the (small) social system that the US have "radical"?  The real radicalization has taken place from the right alone and the Tea Party is succeeding in mainstreaming ideas that are unsustainable and inflexible.