Question: who was the main force behind the kansas nebraska act
[{'answer': 'President Franklin Pierce', 'provenance': [{'wikipedia_id': '17042', 'title': 'Kansas–Nebraska Act', 'start_paragraph_id': 1, 'start_character': 230, 'end_paragraph_id': 1, 'end_character': 255, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Democratic Senator Stephen A. Douglas of Illinois'}]