Barack Obama and Sarah Palin are 10th cousins through a common ancestor, John Smith, a 17th century pastor, according to genealogists.
Ancestry.com found that the two politicians, who could face each other in the 2012 race for the White House, are both related to Mr Smith, a Protestant pastor who was an early settler in Massachusetts.
The website, based in Provo, Utah, also discovered that Mr Obama was a 10th cousin once removed from Rush Limbaugh, the conservative talk radio host and one of the president's most virulent critics. Their common ancestor is Richmond Terrell, a Virginia settler who arrived in America in the mid-17th century.
An Englishman called John Lathrop, exiled to the United States for becoming a minister of an illegal independent church, was cited as the common link between Mrs Palin, Senator Harry Reid, the Senate Majority Leader, and Ann Coulter, a conservative author.
Mr Obama is apparently an 11th cousin of former president, George W. Bush, through common ancestor Samuel Hinckley.
