While a number of scholars have reckoned with the rational-choice model of candidacy for of ice, a great deal of attention has been focused on the likelihood of winning and the overall “opportunity structure” potential candidates face as influential shapers of their decisions. This research does not dispute these factors as formative and dominant, but instead seeks to use a ready-made natural experiment - state laws which prevent candidates from running for more than one of ice at once - to dif erentiate between the ef ects of the “costs” of running for of ice, which are a guaranteed loss of current benefits, and the “risks” of running for of ice, which only forfeit current benefits if the candidate wins. The theoretical argument is that candidates subject to these laws, in which current of iceholders must essentially forfeit their current of ice in order to run for higher of ice, will do so at lower rates due to this increased guaranteed cost. I utilize an original comprehensive dataset of members of the U.S. House of Representatives in every state and district from 1946 - 2016 and model their likelihood of running for U.S. Senate using logistic regression abetted by more simplistic dif erence-of-means tests. While the results are inconclusive, there are several possible avenues by which this research could make a meaningful contribution.