Question: who had the longest tenure as moderator on meet the press
[{'answer': 'Tim Russert', 'provenance': [{'wikipedia_id': '166713', 'title': 'Meet the Press', 'start_paragraph_id': 14, 'start_character': 62, 'end_paragraph_id': 14, 'end_character': 73, 'bleu_score': 1.0, 'section': 'Section::::History.:Under Russert.\n'}]}, {'provenance': [{'wikipedia_id': '166713', 'title': 'Meet the Press', 'start_paragraph_id': 14, 'start_character': 0, 'end_paragraph_id': 14, 'end_character': 315, 'bleu_score': 0.9632870032952191, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1903992711249931097}, 'section': 'Section::::History.:Under Russert.\n'}]}, {'provenance': [{'wikipedia_id': '166713', 'title': 'Meet the Press', 'section': 'Section::::History.:Under Russert.\n', 'start_paragraph_id': 14, 'end_paragraph_id': 14, 'meta': {'evidence_span': ["Network officials, concerned for the show's future, turned to Tim Russert", 'Tim Russert, the network\'s Washington, D.C., bureau chief. He took over as moderator of "Meet the Press" on December 8, 1991, and remained with the program until his death on June 13, 2008, becoming the longest serving moderator in the program\'s history.', 'Tim Russert']}}]}]