TALLAHASSEE, Fla. - U.S. Rep. Katherine Harris holds a double-digit lead over her three opponents in the Republican race for the U.S. Senate nomination in Florida's Sept. 5 primary election, a new poll released Thursday showed. Harris, who is serving her second term in Congress from a district representing the Sarasota area, was favored by 38 percent of 317 likely Republican voters in a random telephone survey taken between Aug. 23-28 by the Quinnipiac University Polling Institute. The survey reported a margin of error of plus or minus 5.5 percentage points.William McBride, a 34-year-old Windermere attorney, was supported by 22...