Question: who steps in if a president is impeached
[{'answer': 'vice president', 'provenance': [{'wikipedia_id': '174647', 'title': 'United States presidential line of succession', 'start_paragraph_id': 1, 'start_character': 639, 'end_paragraph_id': 1, 'end_character': 653, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]