US Republican ex-President George HW Bush will vote for Democrat Hillary Clinton in November, US news website Politico reports.
Mr Bush allegedly made the pledge to Kathleen Kennedy Townsend, niece to US ex-President John F Kennedy.
The former president's office has not confirmed the report, with a spokesman saying he was checking.
Mr Bush, who held office from 1989 until 1993, has not endorsed Republican candidate Donald Trump.
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