MADISON, Wis. (AP) – The new online exchange where people can buy health insurance opens Tuesday.  But advocates for those in Wisconsin who will be shopping for coverage say Dec. 15, not Oct. 1, is the date that concerns them the most.  That’s when the deadline hits to get coverage beginning in January. That date is especially important for 92,000 people being forced off Wisconsin’s BadgerCare Medicaid program at the end of the year. If they don’t sign up for coverage through the exchange by Dec. 15, they will have no insurance at the start of next year.  Jon Peacock, research director for the Wisconsin Council on Children and Families, says there could be a “big bottleneck” around that December deadline.  Both he and state officials encourage people to start shopping for insurance early.