WASHINGTON — A federal judge’s ruling that the Obama health law is unconstitutional has landed like a stink bomb among Republicans, who’ve seen the politics of health care flip as Americans increasingly value the overhaul’s core parts, including protections for pre-existing medical conditions and Medicaid for more low-income people. While the decision by the Republican-appointed judge in Texas was sweeping, it has little immediate practical impact because the Affordable Care Act remains in place while the legal battle continues, possibly to the Supreme Court. HealthCare.gov , the government’s site for signing up, was taking applications Saturday, the deadline in most...