The Johnson-Kendall-Roberts (JKR) theory of contact [Proc. R. Soc. London, Ser. A. 324, 301 (1971)], which has been used to study adhesion of particles, is based on the assumption that the adhesive interactions are short ranged. This is not the case if the particles are charged. In this work, analytical and numerical (finite element) methods are used to analyze the adhesive contact of a spherical elastic insulating particle with uniformly distributed surface charge to a rigid conducting half space. Our results show that the contact radius can be accurately predicted by the JKR theory provided that the mechanically applied force in the JKR theory is supplemented by an appropriate electrostatic force.