Despite being ousted in 1989 after a 35-year reign of terror, during which 20,000 people were tortured, executed or disappeared, some Paraguayans feel as if Gen. Alfredo Stroessner never truly left.

The Colorado Party, the dominant force within the nation’s politics, has governed Paraguay for over seven decades (barring a brief period from 2008 to 2013). Military dictatorships have consolidated ...