It was clear when Obamacare was being debated three years ago that it (now along with the SCOTUS ruling on Medicaid) was going to define federalism in the U.S. for a generation. But how exactly that evolves is going to shake out in the implementation. And right now that's happening most visibly in the decision as to whether states or the federal government will be responsible for a state's exchanges, the new competitive marketplaces for individuals and small businesses being set up under the law. Right now, states that haven't already done so are making their initial decision on this question. There's an interesting confluence, in some corners at least, in the opinions of folks on the left and right on this matter: states should turn the marketplaces over to the feds. For instance, here's the liberal rationale presented over at firedoglake in Most Republican States Wont Build Exchanges and That Is a Good Thing: Meanwhile, conservatives at places like RedState are reaching the same conclusion by asking Will GOP Governors Save us From Obamacare? Thus far there's been more enthusiasm for developing their own marketplaces in Democrat-led states, though some Republican-led states have decided to build exchanges and some Democrat-led states have opted not to. In many ways, the decision is easier for Democratic leaders, however. Yesterday, Politico laid out the tricky political calculus that red state leaders are facing in How red-state governors are opening the doors to Obamacare: What's clear is that, at least for the next few years, there's going to be a mix of state-led exchanges, federal-led exchanges, and federal-state partnership exchanges. How that evolves will be fascinating to watch.