Source: The Brookings Institution

Congress expected each state to create and manage its own exchange, but only 14 (plus Washington, D.C.) agreed to do so. The rest, reflecting hostility to Obamacare or concerns about the complexity of the task, opted to let Washington do all or part of the job in time to open for business on Oct. 1.

Republicans are still pushing for a delay of exchanges, if not outright defunding, saying the technology isn’t ready and raising the specter of identity theft. Democrats say the exchanges may experience some setbacks but will ultimately offer consumers more choice and the security of guaranteed coverage. Over the long term, the system will add competition to the insurance market and empower consumers, supporters argue. Affordability remains the sharpest point of contention: The administration says premiums are lower than expected, offering a good deal especially for lower-income or sick Americans. Critics say the rates come with hefty out-of-pocket costs and severely restricted doctor networks and argue the law is pushing up costs for everybody else.