Which Nevada senator did not win reelection in 2018?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q4167836', 'id': 0, 'label': 'Wikimedia category'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q1227', 'id': 1, 'label': 'Nevada'}, {'type': 'INTERNAL', 'name_': 'Q7703873', 'id': 2, 'label': 'Category:Bridges in Nevada'}, {'type': 'INTERNAL', 'name_': 'Q104230414', 'id': 3, 'label': 'Category:Views from Boundary Peak (Nevada)'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q573205', 'id': 4, 'label': 'Boundary Peak'}], 'links': [{'name_': 'P31', 'source': 2, 'target': 0, 'label': 'instance of'}, {'name_': 'P971', 'source': 2, 'target': 1, 'label': 'category combines topics'}, {'name_': 'P31', 'source': 3, 'target': 0, 'label': 'instance of'}, {'name_': 'P971', 'source': 3, 'target': 4, 'label': 'category combines topics'}]}