An 1888 massacre of aMay Daygathering and an unprecedentedfinancial crisisled to the formation of the first meaningful opposition to develop as reform movements in urban areas, culminating in theRevolution of the Parkthat forced Juárez Celman's 1890 resignation. These developments gathered speed when theCivic Youth Unionbecame theRadical Civic Union(UCR), in 1891. Instability also prompted moderates from within the PAN to advance a diplomat,Roque Sáenz Peña,as the nominee. Roca foiled this move by persuading formerSupreme CourtChief JusticeLuis Sáenz Peña(Roque's father) to run – forcing the young reformist to withdraw. The UCR's appeal, for its part, helped lead PresidentCarlos Pellegrini(who replaced the besieged Juárez Celman) to declare astate of siegea week before the 10 April 1892 elections. The resulting UCR electoral boycott left the ruling PAN as the only party on the ballot, handing its nominee the presidency unanimously.[1]