Agreed.
Also, they're not scared. They can still kill his candidacy, and if they can't, there are plenty of ways to blunt his power. Further, as we saw after Ross Perot got 19% of the vote in 1992, they can throw up institutional hurdles making it impossible for progressive candidates to have a shot at these offices in the future.
Most of all, though, it's hard for me to get excited about this after watching Obama rule as a conservative when he sold us 'hope and change'.