Pennsylvania Rep. Jack Murtha has officially endorsed Hillary Clinton for the Democratic nomination.

Our standard disclaimer about the actual impact -- or lack thereof -- of endorsements in the days after the era of machine politics applies. Still, Murtha does bring a couple of important things to the table. First, as one of the leading antiwar voices in Congress, he might bring Clinton some credibility on the Iraq war that she has lacked so far with certain parts of the Democratic base. Then, also, perhaps much more important than Murtha's ability to move actual votes in Pennsylvania at this point is his superdelegate vote. Barack Obama's been running the table in picking up superdelegates recently, and though this might not stop the tide, it's at least something of a bulwark in Clinton's favor.