October 17, 2012, Written by: Marc Caputo, The Miami Herald – In a sign of the intense interest in the presidential race, about 500,000 Floridians have already cast absentee ballots and that number is growing by the day.More than 1.8 million additional voters have requested the ballots, which are typically mailed in. The heaviest voting so far is taking place in Tampa Bay, Miami-Dade and the so-called Interstate 4 corridor in the center of the state. Generally, whoever wins the I-4 corridor — the swing area of the swing state — wins the election. Overall, Republicans lead Democrats in the number of voted absentee ballots so far, by a 45-40 percent spread. That’s despite the fact that registered Democrats exceed Republicans by a 4-percentage-point margin in the state.