Bill Richardson has decided to endorse Barack Obama for the Democratic nomination, and should make it official this morning. For Obam, this comes as a refreshing change of narrative after two weeks of Tony Rezko and Jeremiah Wright scrutiny. For Richardson, it provides at least a momentary return to relevance — and the potential for a VP nod:

ABC News can confirm that former presidential candidate, Bill Richardson is set to endorse Sen. Barack Obama Friday.

According to Obama campaign aides, Richardson will appear at Obama’s 9:30 am Pacific-time rally at the Memorial Coliseum in Portland, Oregon.

Noting he was “deeply honored” by Richardson’s support Obama said in a released statement, “Whether it’s fighting to end the Iraq war or stop the genocide in Darfur or prevent nuclear weapons from falling into the hands of terrorists, Gov. Richardson has been a powerful voice on issues of global security, peace and justice, earning five Nobel Peace Prize nominations.”

Richardson’s endorsement of Obama over Senator Hillary Clinton is seen as a blow to the Clinton campaign who have a long relationship with the governor. Richardson was Ambassador to the UN under the Clinton administration, and remained friendly with the former President afterward.

This does tend to throw Hillary under the bus. It doesn’t reach the level of egregiousness as Al Gore’s backstab of Joe Lieberman, when his former running mate endorsed Howard Dean after Lieberman graciously delayed entering the 2004 race to see whether Gore wanted to try again after his narrow 2000 loss. However, given the close relationship between Richardson and the Clintons until this year, it looks like Hillary has lost the ability to keep allies in the fold, which will not help in keeping other superdelegates in line.

Richardson’s endorsement helps Obama with Latinos in the party, but the question will be to what extent. Before Bill Clinton set fire to race-based passions in South Carolina, the demographics showed strong Latino support for Hillary — and some support for John McCain as a second choice. The Hispanic community tends to be much more socially conservative than Obama, and the rhetoric from Wright will not set well with a group that sees America in much more positive terms than the sermons given at Trinity United Church. Richardson’s endorsement may offset that, but not by much.

Would it improve if Obama made Richardson his running mate? Richardson has been running for VP since mid-2007, when it became obvious that Obama had become the anti-Hillary in the Democratic primary. He could supply much of what Obama lacks — executive experience, a foreign-policy track record, and better legislative connections. Unfortunately, none of that helped Richardson in the primaries, and for one reason: Richardson is a lousy campaigner. He couldn’t raise money, and despite the best résumé in both parties, he could gain no traction at all against two demonstrably weaker candidates.

That may not matter to Obama. He can campaign well enough on his own, and running mates rarely win or lose elections by themselves. He needs the prestige Richardson brings. And if Richardson endorsed him now, with the Jeremiah Wright scandal in full bloom, it’s likely some quid pro quo is involved.