As governors around the country deliver their annual addresses and legislatures prepare to convene, one of the key policy stories of 2013 is cropping up in state after state—whether to accept federal funds promised by the Affordable Care Act and expand Medicaid coverage.

This sounds like eye-glazing stuff, but it’s fairly straightforward: Costs for Medicaid, which covers certain low-income Americans, are shared between state and federal governments. Obamacare widens access to healthcare coverage in part by raising the income threshold for Medicaid, thus expanding eligibility. And under the law the cost of insuring these newly eligible patients is almost entirely borne by the federal government—the feds will pick up 100 percent of the costs for three years after 2014, with the share sliding down to 90 percent in 2022 and beyond.

It’s designed to be an offer that states can’t refuse. But thanks to the Supreme Court’s ruling on the ACA they are empowered to do so, and with hostility to healthcare reform still running high among Republicans, the future course of Medicaid in states with GOP leadership (as well as some run by Democrats) is very much in doubt. Fortunately, some solid reporting from around the country in recent weeks has kept readers up to speed on key developments—and also helped ensure that the public debate is rooted in credible numbers. Here’s a roundup:

— The most surprising development on this front came earlier this week, when Arizona Gov. Jan Brewer—whose movement conservative bona fides are well-established—endorsed a Medicaid expansion in her state. GOP opposition is often tied to arguments that states will end up bearing a higher share of the costs than the ACA promises. But as The Huffington Post’s Jeffrey Young and John Celock write, Brewer hit on an approach that reflects that concern while still accepting federal dollars to expand healthcare coverage:

“As I weighed this decision, I was troubled that a future president and Congress would reduce matching rates,” Brewer said. “Together with my team, I have crafted a plan that addresses both of those concerns and safeguards Arizona.”

Brewer’s plan includes what she described as a “circuit breaker,” which would automatically shrink the state’s Medicaid program in the event that the federal government were to decrease funding.

“I will not allow Obamacare to become a bait and switch,” she said.

Of course, Brewer can’t act by fiat. The state legislature will need to sign on to the expansion, and Mary K. Reinhart of The Arizona Republic has a good write-up of the mixed response to Brewer’s announcement from Arizona’s Republican lawmakers here. Reinhart’s article also has some interesting backstory on how Brewer came to support Medicaid expansion:

Brewer had previously joined 25 states to push for repeal of the federal health-care overhaul and rejected a state-run health exchange, an online insurance marketplace and another pillar of President Barack Obama’s health-care law.

But she was lobbied hard in recent weeks to support Medicaid expansion by a coalition of hospital CEOs and business leaders, represented by former Brewer adviser and state budget director Peter Burns.

Burns and the Arizona Health Care Coalition last month presented a detailed proposal for Medicaid expansion, complete with the number of uninsured patients for each legislative district.

Brewer’s plan, and her reasoning, is similar to that plan: The health-care system is an important economic driver; voters already approved Medicaid expansion in 2000; AHCCCS is a national model; and hospitals are being “pushed to the brink” by costs for the uninsured.

Hmm. Maybe those Tea Party Republicans aren’t so immune to persuasion by big business after all.

— Brewer’s announcement was surprising not just because many state-level Republicans have opposed Medicaid expansion, but because they have often used questionable estimates of the cost to their states to justify that opposition. Of course, we only know that those estimates are questionable because of some solid local reporting.

In Florida last week, for example, Carol Gentry, editor of the site Health News Florida, got ahold of emails showing that costs cited Gov. Rick Scott had been refuted by the state’s chief economist—and that Scott was aware of the pushback but had continued using the inflated numbers anyway. The higher estimates had been produced by a Scott advisor who apparently assumed that the federal government simply would not provide the boost in funding promised under the ACA.

Greg Marx is an associate editor at CJR. Follow him on Twitter @gregamarx.