WASHINGTON — Talk about stirring a state, and perhaps a nation, to rein in sprawl and ease congestion. Last Monday, the newly-elected centrist Democrat Timothy M. Kaine marched into the General Assembly and told lawmakers that his first priority as Virginia’s governor is giving local leaders the authority to block new housing and business construction if roads cannot handle the increased traffic. What’s most important is not just what Mr. Kaine proposed, but where these Smart Growth ideas could take effect. Virginia lies right next to Washington. From one end of Pennsylvania Avenue to the other, politicians in search of...