According to recent scholarship, parties in a variety of electoral systems can significantly increase their share of the vote with “flanking moves” designed to siphon off opponents’ supporters with appeals to neglected policy concerns. These models do not specify the conditions that enable parties to carry out such maneuvers, however. We maintain that to take advantage of flanking opportunities, parties must undertake two tasks—ideology construction and grassroots mobilization— prior to the emergence of those opportunities. We illustrate our argument with a comparative-historical analysis of the National Party in South Africa and theRepublican Party in the United States. Facing similar strategic contexts after the Great Depression, the two parties responded very differently to opportunities to attract voters through conservative racial appeals during the 1940s
