Prince George’s County voters could tip the balance in Maryland’s two most closely contested ballot initiatives on Election Day. Polls have shown that Maryland voters are closely divided on referendums to expand gambling and legalize same-sex marriage, and Prince George’s residents have been courted heavily in both campaigns. The county’s voters have unofficial veto power over part of the gambling initiative that would allow a Prince George’s casino, and its abundance of religious, socially conservative black Democrats are widely seen as a pivotal demographic in the marriage battle. “This is a really important election for us,” said Pat Myers, an...