David discusses Obama's endorsement from Teddy Kennedy below; it will be valuable to BHO if Kennedy can campaign effectively amongst older voters, Latinos, and labor. Those are three constituencies in which Kennedy has some real juice, and Obama trails Clinton. Also, it gives Obama some old-guard cache.
But color me dubious. I'm just not sure endorsements matter. Imagine the thought process that would be necessary: "Well, I've seen these candidates in debates, on the late night talk shows, on the front page of my newspaper, on the internet, in their ads, on cable TV—I've seen these candidates everywhere in the last few months and have all the information I could possibly need to make a decision. But I'll just do what Teddy Kennedy says." Really? In this supersaturated news environment?
I may be wrong. There may be a number of what political experts call "low-information voters" who use things like endorsements as shortcuts. And perhaps there is a generation of Americans whose allegiance to the Kennedy brothers is so strong that an endorsement matters. I'll concede that—but does anyone care who Senator Sheldon Whitehouse (D-RI, if you were wondering) supports?
While we're on the topic, here is how Clinton's and Obama's Senate endorsements break down: