Jon Huntsman Jr. has not served in at least two different presidencies.
Jon Huntsman Jr. . He has served in the administrations of five U.S. Presidents and was a candidate for the 2012 Republican presidential nomination . He began his career as a White House staff assistant for Ronald Reagan , and was appointed Deputy Assistant Secretary of Commerce and United States Ambassador to Singapore by George H.W. Bush . Later as Deputy U.S. Trade Representative under George W. Bush , he launched global trade negotiations in Doha in 2001 and guided the accession of China into the World Trade Organization . In 2009 , he was appointed United States Ambassador to China by Barack Obama .