Will Castro's endorsement bring Republican votes to Underwood?

Congressional candidate Robert Underwood waves to motorists in Yigo. Facebook photo

Guam voters go back to the polls today for a runoff election that will settle the congressional race between two Democrats -- Delegate Michael San Nicolas and former congressman Robert Underwood.

The candidate who wins the majority vote (50 percent plus one) wins the hotly contested seat-- a nonvoting position in the U.S. Congress.