[14] On October 15, 1991, however, the Supreme Court declared Mercado's electoral opponent Rosette Yñiguez-Lerias as having won the 1987 election by 146 votes.

[15][8] Just after the 1992 Philippine general election, Mercado was the chair of the House Agrarian Reform Committee.

[1] Mercado ran for governor in the 2001 Philippine general election, losing to Rosette Lerias of the Nationalist People's Coalition, with him running with Lakas-CMD again.

[18] On October 12, 2021, Mercado was appointed by President Rodrigo Duterte to become the Secretary of the Department of Public Works and Highways.

[19] Because of the appointment, he withdrew his re-election bid for the congressman of Southern Leyte's 1st congressional district, which was then newly redistricted.