Legislative bargaining often is additive: Supporters of legislation A endorse legislation B so that its advocates will reciprocate by supporting A. By this process a coalition (and government) grows. However, congressional bargaining about replacing/mending the ACA might become an exercise in subtraction. The debate is making clear that the expansion of a 52-year-old program, Medicaid, is the most important aspect of the 7-year-old ACA. Twenty Republican senators represent states that expanded Medicaid and face budget agonies if the expansion is abruptly reversed. But many Republican representatives and senators believe it should be. Perhaps this is a difference that can be split. If not, adding the support of some legislators will subtract that of others.