Standing in the expansive basement family room of a Fulton mansion, Dr. Eric S. Wargotz explained why he thinks 2010 will be so kind to Republicans that he's got a chance to replace four- term U.S. Sen. Barbara A. Mikulski, arguably Maryland's most popular Democrat. "I'm running because I believe I can do it," said Wargotz, 53, a first-term Queen Anne's County commissioner. "I see an opening here. Look at Scott Brown," he said, referring to the once-obscure Massachusetts Republican state senator catapulted to national celebrity by winning a special election for the late Sen. Edward M. Kennedy's Senate seat....