The party had strong support in the Southeastern region of the country, including the South Gyeongsang Province and the city of Busan.

Following the June Struggle of 1987, and the June 29 Declaration, which Roh Tae-woo promised direct, democratic election of the president in the upcoming presidential election in December of that year, speculation for the potential candidacy of Kim Dae-jung for the presidency grew.

The Declaration also promised amnesty to Kim Dae-jung, who was under the house-arrest and was barred from engaging in any political activity under the fabricated charge of "inciting rebellion" since 1971.

Despite the effort to present the single opposition candidate for the 1987 presidential election, the negotiation between two politicians broke down.

In the following 1988 legislative election, Reunification Democratic Party received a disappointing result.