Rick Davis, the manager of Senator John McCain’s presidential campaign, is a typical Washington insider in many ways, having long worked as both a lobbyist and a political operative along the intersection of politics, policy and money. Now Mr. Davis is overseeing new lobbyist-related guidelines that the campaign has issued in an effort to safeguard Mr. McCain’s reputation as an opponent of special interests. The plan, among other things, bars “registered” lobbyists, those who must file disclosure reports listing their clients, from working on the campaign. Mr. Davis, who last worked as a registered lobbyist in 2005 and took a...