Make the text more logical: They both played main roles during the campaign for the 1993 plebiscite, which represented the hitherto only real opportunity for a return of the monarchy since the proclamation of the republic, in 1889.
They both played main roles during the campaign for the 1993 plebiscite in 1889. The 1993 plebiscite represented the hitherto only real opportunity for a return of the monarchy since the proclamation of the republic.