Stephenson entered the political fray on the island when he was nominated as the candidate for the Castries North-East Constituency. Having won the seat in the 1982 election, he was then appointed as a Cabinet Minister, serving as the Minister for Community Development, Social Affairs, Youth, Sports, and local Government.
He faced the electorate again in 1992, and having won his seat again was appointed to the Cabinet as the Minister for Health, Local Government, Information and Broadcasting.
The UWP once again won a majority of seats in the 2006 election, and a new government under Sir John Compton. King was named Minister for Health and Labour Relations.
Compton’s illness in May 2007 prompted King to be named Acting Prime Minister. In a cabinet reshuffle in early June 2007, he became Minister of Finance (inclusive of International Financial Services), External Affairs, Home Affairs, National Security, Labor, Information and Broadcasting.
The King administration suffered defeat in the 2011 general elections, obtaining only 6 out of 17 seats in Parliament.