The "Mayor" of Richmond is largely ceremonial, and he had little to do with all the "good things" that happened in Richmond.
The Lt. Governor is really the president of the Senate, but only to vote if it's a tie. Otherwise, he does nothing.
Kaine really has little real executive experience -- but he does have a lot more than Obama.
On the other hand, he's only won one state-wide election, and he has no foreign policy or military experience.
He’s just a regular guy here’s an idea for the acceptance speech.
http://www.takegreatpictures.com/content/images/citizen_kane_1.jpg
FWIW, that was true while Kaine was mayor. That's changed now that the Mayor (currently Doug Wilder) is elected.
But your point applies correctly to Kaine.