Most candidates running in a general election tend to move their campaigns toward the a. far right of the party line b. far left of the party line c. current domestic issues d. ideological center e. current international issues

Ideological center

Its  because the candidates aims at addressing societal concerns. There are however various approaches to the problems and concerns. The solutions always attracts  ideological differences. To win over all the ideological affiliations, candidates therefore tend toward the center.