Question: when did presidential candidates start choosing running mates
[{'answer': 'during the American Civil War', 'provenance': [{'wikipedia_id': '216817', 'title': 'Running mate', 'start_paragraph_id': 8, 'start_character': 78, 'end_paragraph_id': 8, 'end_character': 107, 'bleu_score': 1.0, 'section': 'Section::::In United States politics.\n'}]}, {'provenance': [{'wikipedia_id': '216817', 'title': 'Running mate', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 831, 'bleu_score': 0.8404007486081191, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7272455079955235933}, 'section': 'Section::::In United States politics.\n'}]}]