Republican opposition to the Medicaid expansion appears to be fading fast.

New Jersey Gov. Chris Christie will announce his support for the expansion this afternoon, according to the New Jersey Star-Ledger, following a similar statement from Florida Gov. Rick Scott last week. He followed early February announcements from governors in Ohio and Michigan.

Taken together, these eight states will extend Obamacare's coverage expansion to 3.2 million Americans, according to this analysis from the Urban Institute. They will take in a cumulative $90 billion in federal funds to do so.

The quick succession of governors to come out in favor of this part of the Affordable Care Act suggests that, when it comes to the Medicaid expansion, the lure of federal dollars may trump anti-Obamacare politics.

When you look at the deal that the states are getting, it's pretty easy to see why. The federal government will spend an additional $800 billion on Medicaid under the health-care law to cover all those earning less than 133 percent of the federal poverty line (about $15,000 for an individual).

In return, the states only need to put up $8 billion of their own money. Drawing down $100 in federal match for every $1 a state puts in? That's a way better deal than the regular Medicaid system, where states usually get back $1 or $2 in return for each dollar they spend on the program.

In New Jersey, for example, Urban Institute analysts expect that the state will bring in $15 billion, while spending $1.4 billion of its own funds, should it participate in the expansion.

For the first three years, the program looks even better: The federal government foots 100 percent of the bill for those newly eligible. After that, the match tappers off to 90 percent.

That money will go toward covering much of the uncompensated care that happens now, the doctor visits and hospital trips that end with an unpaid bill. Usually, that tab is picked up by local governments and hospitals.

To be sure, there are many Republican states that say they will not move forward on the provision. But even some of those are looking for ways to provide more comprehensive coverage, such as Wisconsin. There, Gov. Scott Walker is looking at a plan that would cover those below the poverty line with Medicaid, while those right above it would have access to private exchange subsidies.

The drafters of the Affordable Care Act never expected that the administration would need to convince governors to expand Medicaid; it was simply required of all 50 states. The Supreme Court changed that in its June ruling, making the provision optional. Looking back, what they did come up with has done surprisingly well at bringing some of the health law's fiercest opponents on board.