Complex sentence: PDR grew out of the PRI in 1986 as the leftists who created the "Corriente Democrática" (Democratic Current) within PRI split off and came quite close to claiming the presidency in 1988.
Split into simpler sentences: PDR grew out of the PRI in 1986 as the leftists who created the "Corriente Democrática" (Democratic Current) within PRI split off. It came quite close to claiming the presidency in 1988.