Measurements of the optical light curve, polarization degree, and position angle of OJ 287 by the 1.8 m Perkins telescope during the EHT campaign. Top panel:R-band optical flux density as a function of time. Middle panel: Degree of polarization in the R band (black), at 221 GHz from ALMA (green) and for individual jet components, P1 (red), P2 (blue), and P3* (orange). Bottom panel: Polarization position angle evolution in the R band (black) and the source-integrated value measured by ALMA at 221 GHz (green) and for the same jet components (P1, P2, and P3*). The gray-shaded region highlights the period corresponding to the EHT observations.