In 1815 Hughes was elected to the
Maryland House of Delegates as a
Democratic-Republican, and he served one term. In 1816 he declined an opportunity to run for the
United States House of Representatives, deferring to his father in law, who was elected. Later in 1816 Monroe dispatched Hughes to New Granada (now
Colombia) to negotiate with
Spanish authorities, who had confiscated several American ships and their cargo and imprisoned the crews. The authorities in New Granada had sold off the ships and cargo by the time Hughes arrived, but he was able to secure the release of most of the 50 crew members, excepting those who had died, escaped or already been freed. Monroe then appointed Hughes as Chargé d'affaires in
Stockholm, where he served until 1825. During his time in Sweden, Hughes worked to implement and expand on trade agreements negotiated by his predecessor,
Jonathan Russell. In Stockholm he rented rooms from Baroness Emerentia Augusta Charlotta von Lantingshausen Rålamb and her husband Claes Gustaf Rålamb in the Lantinghausen Palace opposite
Stockholm Palace. After John Quincy Adams became president, he honored Hughes's request for a new diplomatic posting, nominating him to serve as chargé d'affaires in The Netherlands. In 1830 the United States decided to upgrade the post in The Netherlands to Minister Plenipotentiary, but disappointed Hughes by nominating William Pitt Preble of
Maine. At the time the King of The Netherlands had agreed to mediate the Maine-
New Brunswick boundary dispute between the United States and
Great Britain, and the Senate determined that U.S. interests would be better served by someone with first hand knowledge of the issue. After Preble's appointment was confirmed Hughes was nominated to return to Sweden as Chargé d'affaires. He served until 1842 and continued his work to enhance trade between Sweden and the United States. Hughes's wife died in 1832, and his father in law and son Charles in 1839. He also had a daughter, Margaret (January 9, 1819—August 1, 1884), who had settled in Baltimore after her mother's death. Margaret was the second wife of Senator
Anthony Kennedy. As a result of these personal events Hughes began to ask for a new assignment that would enable him to change his location, and in 1842 President
John Tyler appointed Hughes to a second tour as Chargé d'affaires in The Netherlands. He served until 1845, when the incoming administration of President
James K. Polk and Secretary of State
James Buchanan appointed
Auguste Davezac to take his place. ==Retirement, death and burial==