Richardson should have endorsed Obama before the Texas primary if it were to have any electoral effect. Obama's goals now are to run out the clock on Michigan and Florida, tie up in red tape any solutions to that problem , and get the Wright business off the page. The Richardson endorsement and latest passport flap help in the latter objective.
Richardson, like George Tenet, is a classic bureaucratic climber-upper. The VP slot is perfect for him, but there's only so much diversity for the electorate to handle at one time. I believe there are better choices, like Biden.