OKLAHOMA CITY — Despite bitter resistance in Oklahoma for years to President Barack Obama’s health care overhaul, Republican leaders in this conservative state are now confronting something that alarms them even more: a huge $1.3 billion hole in the budget that threatens to do widespread damage to the state’s health care system.

So, in what would be the grandest about-face among rightward leaning states, Oklahoma is now moving toward a plan to expand its Medicaid program to bring in billions of federal dollars from Obama’s new health care system.

What’s more, GOP leaders are considering a tax hike to cover the state’s share of the costs.

“We’re to the point where the provider rates are going to be cut so much that providers won’t be able to survive, particularly the nursing homes,” said Republican state Rep. Doug Cox.

Despite furious opposition by conservative groups, Republican Gov. Mary Fallin and some GOP legislative leaders are pushing the plan, and support appears to be growing in the overwhelmingly Republican Legislature.

A bust in the oil patch has decimated state revenues, compounded by years of income tax cuts and growing corporate subsidies intended to make the state more business-friendly.

Oklahoma’s Medicaid agency has warned doctors and other health care providers of cuts of up to 25 percent in what the state pays under Medicaid.

“We are nearing a colossal collapse of our health care system in Oklahoma,” warned Craig Jones, the president of the Oklahoma Hospital Association. “We have doctors turning away patients. We have people with mental illnesses who are going without treatment. Hospitals are closing, and this is only going to get worse this summer if the Legislature does not act immediately to turn this around.”