With President Bill Clinton a reported no-show for Barack Obama's acceptance speech tomorrow, this was the nominee's one shot to congratulate him in person on his address. Smart move. (As was his reference to the 1992 slogan "putting people first," a nice nod to the legacy Clinton is reported to be concerned about.)
The counter-argument, of course, is that Obama has been a touch too over-exposed of late, and that his surprise appearance might have upstaged Sen. Joe Biden's prime-time debut as vice presidential nominee.
The first count can be dismissed, I think, since we know Obama can be over-exposed even when he's on vacation. If we're going to have Obama-centric coverage, it's better for Democrats to have his loose, affable matter (e.g., Hillary "rocked the house") be part of that instead of leaving all the definition of Obama to the McCain campaign oppo team.
And Biden's speech, well-written though it was, contained enough verbal tics that it might have fallen just short of taking the night to a satisfying finish on its own. Obama's completion of the circuit not only allowed America to see all the constituent parts of the Democratic Party on the stage at once, but did the same for Democrats. After two days of programming at the Pepsi Center that, at times, felt oddly indifferent, Wednesday's energizing close was likely a change that more than a few delegates were waiting for.