The Centers for Medicare & Medicaid Services Innovation Center (CMMI) has set the goal for 100% of traditional Medicare beneficiaries to be part of an accountable care relationship by 2030. Lack of meaningful financial incentives, intolerable or unpredictable risk, infrastructure costs, patient engagement, voluntary participation, and operational complexity have been noted by the provider and health care delivery community as barriers to participation or reasons for exiting programs. In addition, most piloted and implemented population-based total cost of care (PB-TCOC) payment models have focused on the role of the primary care physician being the accountability (that is, attributable) leader of a patient's multifaceted care team as well as acting as the mayor of the "medical neighborhood," leaving the role of specialty care physicians undefined. Successful provider specialist integration into PB-TCOC models includes meaningful participation of specialists in achieving whole-person, high-value care where all providers are financially motivated to participate; there is unambiguous prospective attribution and clearly defined accountability for each participating party throughout the care journey or episode; there is a known care attribution transition accountability plan; there is actionable, transparent, and timely data available with appropriate data development and basic analytic costs covered; and there is advanced payment to the accountable person or entity for management of the care episode that is part of a longitudinal care plan. Payment models should be created to address the 7 challenges raised here if specialists are to be incented to join TCOC models that achieve CMMI's goal.