On the practical side, the administration has to improve customer service for millions of Americans trying to navigate the new system. There's also a concern that premiums may rise for 2015, since many younger, healthier people appear to have sat out open enrollment season. On the political front, congressional Republicans remain implacably opposed to "Obamacare," even as several GOP governors have accepted the law's expansion of safety-net coverage under Medicaid. Opposition by congressional Republicans means they can be expected to continue to deny additional funds for implementation. The website stumbled early in the day - out of service for nearly four hours as technicians patched a software bug. The system came back up shortly before 9 a.m. EDT, then another hiccup in early afternoon temporarily kept new applicants from signing up. The system, overwhelmed by computer problems when launched last fall, has been working much better in recent months and officials said it was operating at full capacity on Monday. At Chicago's Norwegian American Hospital, people began lining up shortly after 7 a.m. to get help signing up for subsidized private health insurance. Lucy Martinez, an unemployed single mother of two boys, said she'd previously tried to enroll at a clinic in another part of the city but there was always a problem. She'd wait and wait and they wouldn't call her name, or they would ask her for paperwork that she was told earlier she didn't need, she said.