A veteran member of the People's United Party, Marin served as the deputy prime minister under George Cadle Price as well as the deputy leader of the Opposition.

Marin became Deputy Leader of the Opposition and then Leader of the Opposition during the first Manuel Esquivel government after Price was unexpectedly defeated for re-election in December 1984.

After Price stepped down as PUP leader in 1996, Marin stood for election to succeed him.

[2] After leaving office, Marin along with fellow former Belizean Rep. Jose Coye was charged with conspiracy to "misappropriate the value of 56 parcels of land in the Caribbean Shores area."

However, in February 2013 the Caribbean Court of Justice dismissed the case based on lack of evidence.