Although she was not active in politics during her exile in the United States and Spain, Moscoso accompanied her husband in his political career and vowed to defend his political goals after his death in 1988. Upon returning to Panama in 1990, she helped form the Arnulfista Party (named after Arnulfo Arias) in 1990. Moscoso made an attempt to win the presidency in 1994, but was defeated by Ernesto Pérez Balladares. Between 1994 and 1999, Moscoso worked to consolidate and strengthen the Arnulfista Party. Although she was the symbolic leader of the party, she faced opposition from other politicians who argued that a seasoned and experienced public official should contend for the presidency in 1999. In early 1999, she successfully defeated a primary challenge and was named presidential candidate of the Arnulfista Party. In part, her victory resulted from her strong and active opposition to Pérez Balladares's effort to amend the Constitution to permit presidential re-election. Moscoso helped put together a coalition of opposition parties to block constitutional reform in the Parliament. Elections were held on 2 May 1999, and Moscoso won 44.8% of the vote. She defeated Martín Torrijos, son of General Omar Torrijos—the man that had ousted Arnulfo Arias from power in 1968. Martín Torrijos was supported by the PRD, and he obtained 37.8% of the vote. She was inaugurated on 1 September 1999.