Democratic challenger Tom Foley attacked Republican hopeful Bill Ernst last week . Ernst called his comments offensive in an interview with Fox News on Monday . Ernst is locked in one of the most competitive Senate races this year in Iowa . A poll released Monday showed Ernst and Democratic challenger Bruce Smith tied .
Democratic Sen. Tom Harkin attacked GOP hopeful Joni Ernst last week . Ernst called his comments offensive in an interview with Fox News on Monday . Ernst is locked in one of the most competitive Senate races this year in Iowa . A poll released Monday showed Ernst and Democratic challenger Bruce Braley tied .