There are a number of sites here that discuss that topic.
http://www.google.com/#hl=en&source=hp&q=tea+party+movement+affected+incumbent+Republicans+and+Democrats+in+the+primary+races&btnG=Google+Search&aq=f&aqi=&aql=&oq=&gs_rfai=&fp=e6c57a2ab5279010
How has the tea party movement affected incumbent Republicans and Democrats in the primary races?
2 answers
The Tea Party has appealed to the Facist Old Xenophobe viewers and Pundits, and greatly distorted what the land of immigrants mean to the Free world. Incumbents have to fight that distortion with truth, or step lightly over those issues.