The failures of several co-ops and United Healthcare’s announcement that it is considering withdrawing from many or all Marketplaces in 2017 have raised some concerns. However, the Marketplace experiences of co-ops and United Healthcare indicate that they have not been major players in many areas, and their exits will not be overly disruptive. Blue Cross Blue Shield insurers, Medicaid insurers, and provider-sponsored insurers are more frequently driving Marketplace competition. We conclude that the recent revelations regarding United Healthcare and the co-ops are not significant threats to the Marketplaces and the ACA in general.