In another sign that the politics of Obamacare continue to shift, the Medicaid expansion is now all but certain to come to another big state whose Republican governor had previously resisted it: Pennsylvania.

The federal government has approved Pennsylvania Governor Tom Corbett’s application for the state’s own version of the Medicaid expansion, without a handful of the conditions Corbett had hoped to impose, Dem sources tell me.

Corbett just announced that he will accept the expansion that has been offered, perhaps with some last-minute changes — expanding coverage and subsidies to as many as half a million people.

This comes after months of jockeying between Corbett and the federal government. Corbett had pushed for a version of the expansion that would have imposed various conditions designed to make it more palatable to conservatives and to achieve political distance from Obamacare — while simultaneously taking all that federal money. Among them: Using the cash to pay for private coverage for the poor.

According to a Dem familiar with the deal, the version the feds signed off on does not give Corbett some of the things he wanted. In various ways, it is not a true “Private Option,” like the one in Arkansas. Corbett previously dropped the work requirement he’d sought, and did not get a weakening of consumer protections in Medicaid or a “lockout” provision that would have nixed coverage to those who miss a premium payment, the Dem confirms.

To be sure, the deal might still have some provisions that health reform advocates dislike. Still, those could presumably be tweaked by a future Dem governor.

If Corbett does take the final deal, it will amount to more confirmation that the politics of Obamacare are considerably more complicated than the simplistic epic-disaster-for-Dems pundit narrative has it.

Giving government health coverage to poor people is supposed to be difficult politically, because voters — particularly whites — tell pollsters they don’t think the law’s redistributive effects are good for them or for the country. And there are certainly signs that Dems in red states, even ones where the uninsured rate has dropped precipitously, don’t think they can campaign on that as an achievement.

However, the Medicaid expansion has created political complications for Republicans, particularly in swing states. It is broadly popular and the argument against taking all that federal money to cover one’s own constituents is a tough one to make. Multiple GOP Senate candidates  continue to refuse to say whether they oppose allowing the expansion to proceed in their states.  The Republican governors who accepted the expansion are faring better in polls than GOP governors who didn’t.

In Pennsylvania, the Medicaid expansion has solid majority support, and Corbett’s Dem opponent has been hamming him over the lag in accepting it. Corbett had fallen well behind for reelection.

The details of the final deal will matter. But broadly speaking this looks like another sign of just how hard it is for Republican governors in non-deep-red states to resist the expansion — and of how the politics of this issue continue to change.

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UPDATE: Corbett’s announcement is right here.

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.