THE LIEUTENANT GOVERNOR OF Maryland has just one key responsibility under the law: to finish out the term of the state's chief executive if he or she no longer can serve. But a good lieutenant governor can carve out a meaningful role in the administration of the state -- and that potential is what voters should be looking for in a candidate. Both Democrat Anthony G. Brown and Republican Kristen Cox have experience in government. He served eight years in the state legislature; she's been a Cabinet secretary since 2003. But of the two, Mr. Brown has the experience and...