I like primaries. Like many others I question the conventional wisdom which resists them. Locally the primary fight between Patrick Murphy and Andy Warren forced the Murphy campaign to step up their operation and get their act together earlier than they would have otherwise, and presumably helped get his name recognition up to.
Credible primary challenges to incumbent senators would seem to play perfectly into some of the Beltway conventional wisdom narratives - the power of incumbency is too strong, elected representatives should be responsive to their local constituents - which is another reason why the resistance to the Lieberman primary is so puzzling.
Now we see that Lieberman literally has no operation in place. He hasn't bothered to maintain the relationships in Connecticut one needs to keep a network in place.