John Judis points to another reason why moderates are an endangered species:
[The Club For Growth] and its network have yet to unveil their overall strategy for 2014, but some of its members groups have already threatened to back primary challenges to Chambliss and South Carolinian Lindsay Graham. And the threats have had some effect. Chambliss incurred the network’s wrath last summer for attempting to work out a bipartisan compromise on the debt ceiling. After the election, he annoyed them by downplaying his commitment to the pledge, circulated by Grover Norquist, not to raise taxes. "I care more about my country than I do about a 20-year-old pledge." But by this week, he had tweeted that he is "not in favor of tax increases." Chambliss’s decision was not the result of pressure from Norquist, but of the looming threat of a primary challenge from the right.
If the Club and its network remain active for 2014 and 2016 elections, they will almost certainly make it more difficult for the Republicans to retake the Senate and to win back the Presidency.
The Dish 