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Incumbent Democratic United States Senator  Tom Harkin  sought re-election to a third term in the United States Senate and he was challenged by United States Congressman Jim Ross Lightfoot from  Iowa  's 3rd congressional district .
 Tom Harkin, Iowa
Please list all entity pairs containing a certain relationship in the given options.Output format is "word1, word2; word3, word4". 
Option: cities of residence, top members employees, members, alternate names, origin, state or provinces of residence, title of person, spouse, city of headquarters, NA, founded by, state or province of headquarters, employee of, countries of residence, country of birth, founded, subsidiaries, country of headquarters 
Text: {0} 
Answer:
 Tom Harkin, Iowa