Using simulations based on a new economic model, this brief empirically examines the pivotal mechanisms of the Affordable Care Act, such as the individual mandate, employer mandate, and premium subsidies, to inform the debate over repealing and replacing the Affordable Care Act. The research suggests that the ACA, if left intact, in the long run significantly reduces the uninsured rate. The simulations also suggest that the employer mandate is not a crucial pillar for the success of the ACA. The analysis indicates it is the premium subsidy, rather than the employer mandate or the individual mandate, that is crucial for the success of the ACA, in terms of expanded coverage. The brief concludes with a look at the key elements of the main legislative proposals Congressional Republicans have offered to replace the ACA, including the American Health Care Act.