President Barack Obama’s plan to extend private health coverage to the uninsured entered a new uncertain phase on Saturday as U.S. government-backed online insurance marketplaces opened their 2015 plans to millions of potential enrollees. The HealthCare.gov website relaunched with little fanfare and appeared to work smoothly early in the day, a far cry from technical glitches that shut down the operation within minutes of its opening a year ago and drove Democrat Obama’s signature domestic policy to the brink of disaster, exposing him to criticism from Republicans who have campaigned for its repeal.