As the full Senate readies to debate and vote on legislation that would grant the District a voting seat in the House of Representatives, voting rights activists are focusing on two key senators — Sen. Jim Webb (D-Va.) and Sen. Arlen Specter (R-Pa.). According to people close to the lobbying effort, the legislation has garnered enough votes for a simple majority, but is still short of the votes needed to prevent a filibuster. And while…