MADISON, Wis. (AP) – Gov. Scott Walker says Wisconsin will not set up a health insurance exchange under President Barack Obama’s Affordable Care Act.        Instead, Walker told the Obama administration Friday that Wisconsin will leave that responsibility to the federal government.   Walker’s highly anticipated decision was not unexpected given his long opposition to the law. He stopped implementation last year on the hopes the law would be overturned either by the U.S. Supreme Court or Republicans following the November election.  Neither happened.   Walker announced his intention Friday despite the federal government late Thursday giving states an additional month to decide.