Mike Allen blogging over at Ben Smith describes freshman Pennsylvania Senator Bob Casey's Obama endorsement today as a "big break for Obama" and something that will "help Obama with Roman Catholic voters," since Casey's a Roman Catholic. I'm not sure I agree. Has there been any senatorial endorsement in this race that's really affected a primary's outcome? Senators tend not to have the kind of local support networks and political machines that mayors or governors can deploy on behalf of their choice. And in terms of Casey's star power throughout the state -- well, reviews of his first year in office in the Pennsylvania newspapers this winter tended to use words like "subdued," "low-key" (read: invisible), and "Senator who?" An excerpt:

"Of this freshman class, he is definitely the name that doesn't usually come up in conversations or sort of in general reading of news," said Jennifer Duffy of the Cook Political Report, an independent newsletter.

"At least in the beltway, he hasn't kind of established himself as a presence, whether it's on any given issue," she said.

Update: I see Noam disagrees. Parsing Casey's influence in different parts of the state still seems to me to be overthinking it a little bit: The race has so super-saturated the media by now that it's hard to imagine a significant proportion of voters making their minds up thanks to Casey's recommendation (unlike when an official endorses a candidate a lot of voters just don't know), and Casey hasn't grown his influence this year. But never let it be said we don't provide you with contrasting points of view.

Update 2: A valued reader writes in to note that the "Bob Casey" franchise in Pennsylvania goes back a lot further than just this Bob Casey, and therefore has a good deal more weight.

Eve Fairbanks