We study the leading electroweak corrections in the precision measurement of the strange form factors. Specifically, we calculate the two-boson exchange (TBE), two-photon exchange (TPE) plus γZ exchange (γZE), and corrections with Δ(1232) excitation to the parity-violating asymmetry of the elastic electron-proton scattering. The interplay between nucleon and Δ contributions is found to depend strongly on the kinematics, as δΔ begins as negligible at backward angles but becomes very large and negative and dominant at forward angles, while δN always stays positive and decreases monotonically with increasing ε. The total TBE corrections to the extracted values of GEs+βGMs in recent experiments of HAPPEX and G0 are, depending on kinematics, found to be large and range between 13% and −75%, but are found to be small in the case of A4 experiments.

• Received 21 November 2008

DOI:https://doi.org/10.1103/PhysRevC.79.062501