This pioneering study of electoral fraud and reform focuses on Costa Rica, a country where parties gradually transformed a fraud-ridden political system into one renowned for stability and fair elections by the mid-twentieth century. Lehoucq and Molina draw upon a unique database of more than 1,300 accusations of ballot-rigging to show that, independently of social structural constraints, parties denounced fraud where electoral laws made the struggle for power more competitive. They explain how institutional arrangements generated opportunities for several executives to assemble legislative coalitions to enact far-reaching reforms.