The surprise endorsement of Barack Obama by John Edwards more than anything helps Barack Obama put an exclamation point on the Democratic primary. In one swift move Obama has trumped Hillary Clinton’s win in West Virginia last night.

I am sure the speculation will now begin about a potential Obama-Edwards ticket, but in a more practical sense, Edwards built his campaign on white blue collar voter, which is the exact group that Obama has had trouble connecting with all through the primary season.

As a candidate, Edwards was the favorite candidate of labor, and you can expect him to be a powerful speaker this fall on behalf of Obama with the exact group that Clinton bases her electability claims on. If the superdelegates needed another huge signal to open the floodgates and support Obama, Edwards’s endorsement should do the trick.

There is no stronger indicator of Clinton’s unelectability than the fact that none of the other former Democratic candidates has endorsed her. Obama has gotten the endorsement of both John Edwards and Bill Richardson. Both of these Democrats will be powerful surrogates during the fall campaign.