In the old days of political campaigning (>10 years ago) "voter targeting" typically meant blanketing a geographic area with mail, phone calls, and volunteers. The targeted geographies were chosen based on assumptions about voter demographics, income, or nearby employers. It was better than doing nothing at all, but it was still far from efficient.
Advances in technology and data availability have made this type of targeting obsolete, even for the lowest-level office seekers.