About this poll Results are based on a survey of 500 likely Maryland Democratic primary voters. The poll was done by Opinion Works of Annapolis for the Baltimore Sun and the University of Baltimore's College of Public Affairs and Schaefer Center of Public Affairs and Schaefer Center for Public Policy. The survey was conducted by telephone, both land-based and cellular, by trained interviewers from May 29 to June 6. Voters were randomly selected for interviews from a voter file provided by the State Board of Elections. The margin of error is plus or minus 4.4 percentage points