Last year’s launch of the Asian Infrastructure Investment Bank (AIIB) is appropriately viewed as a diplomatic and strategic victory for the Chinese government. In the face of growing U.S. indifference to multilateral development institutions, China is stepping up. The circumstances around the creation of the AIIB have usefully brought to light a longer trend that will ultimately lead to a diminution of U.S. leadership in the multilateral development system, brought about as much by the United States itself as by external challengers. China was successful in attracting so many countries to join the AIIB by offering more infrastructure financing at a time when the prospect for additional financing appeared limited within the core MDBs, in large part due to U.S. resistance. The task for U.S. officials in the years ahead will be to accommodate a larger role for emerging countries, particularly China, in the multilateral development bank system, but to do so from a position of strength and with ambition for the MDBs in U.S. policy. The alternative, in which the United States neither makes space for new voices nor promotes the MDBs themselves, will inevitably lead to a weaker system that will harm the United States and the global good.