Just as millions of people are gaining insurance through Medicaid, the program is poised to make deep cuts in payments to many doctors, prompting some physicians and consumer advocates to warn that the reductions could make it more difficult for Medicaid patients to obtain care. The Affordable Care Act provided a big increase in Medicaid payments for primary care in 2013 and 2014. But the increase expires Thursday ? just weeks after the Obama administration told the Supreme Court that doctors and other providers had no legal right to challenge the adequacy of payments they received from Medicaid.