While Obamacare politics have recently cooled on the Hill — and the relative ease of the confirmation hearings of Sylvia Mathews Burwell to lead the Department of Health and Human Services is proof of that — the president's health-care law will still be a big issue in the midterm elections with control of the Senate at stake.

This is the third election cycle since the Affordable Care Act was passed, and both the Republican and Democratic Senate campaign arms say the races will be settled on much more than Obamacare. But Republicans are counting on the law being a drag for Democrats, while Democrats see Republicans moving onto other topics.

"That’s not to say the issue will not be a factor and could become a bigger factor as the implementation continues, but right now we are at a moment where the significance is waning," said Matt Canter, deputy executive director for the Democratic Senatorial Campaign Committee.

Bob Blendon, a Harvard University expert on public opinion toward health policy, told me that Obamacare is especially unpopular in the states with 12 competitive Senate races identified by Charlie Cook. "Republicans will be running negative against it because the public opinion is not anywhere as positive as it is national, where it isn't terrific," Blendon said.

There are some Senate races, though, where the politics of Obamacare are a little more complicated.

Kentucky: The Obama care paradox
Sen. Mitch McConnell (R) vs. Alison Lundergan Grimes (D)

Kentucky is about as big of an Obamacare paradox that you could find: the state's exchange is working well, but Obamacare remains unpopular in the state. Kentucky is home to Senate Minority Leader Mitch McConnell and Sen. Rand Paul, and it’s also home to one of the more successful Obamacare health insurance exchanges.

The exchange, which worked pretty smoothly from the start of October enrollment, signed up about 83,000 in private health individual plans and another 330,000 for Medicaid. Democratic Gov. Steve Beshear, in light of the exchange's success, has become a national cheerleader for the health-care law.

Kentucky’s exchange may be working well, but Obamacare is still unpopular in the conservative state. In a NBC/Marist poll this month, 57 percent of Kentuckians said they viewed Obamacare unfavorably, while 22 percent had an unfavorable view of the exchange. But nearly another 50 percent said they hadn’t heard of the exchange or weren’t sure how they felt about it.

With McConnell eyeing the majority leader spot if Republicans take back control of the Senate, the Kentucky race will hinge on much more than Obamacare. But Grimes may want to have a better answer the next time she's asked whether she would have voted for the health-care law.

North Carolina: Outside ad money pouring in
Sen. Kay Hagan (D) vs. Thom Tillis (R)

Hagan, who was elected in 2008, is thought to be one of the most vulnerable Democratic incumbents. The conservative group Crossroads GPS this week announced a $3.5 million ad buy in North Carolina over the next month, with the first round of ads hitting Hagan over cancelled health insurance policies.

Still, North Carolina has some of the most robust exchange enrollment of any the 36 states using the federal Web site, HealthCare.gov. About 357,000 North Carolina residents signed up in exchange plans through the end of the 2014 open enrollment period — Florida and Texas were the only states with a federal exchange that signed up more people.

Hagan has fought back against the Obamacare attacks, calling out state Republican leaders – including Tillis, the North Carolina House speaker  – for rejecting the law’s expansion of Medicaid to low-income adults. About 500,000 adults earning under 138 percent of the federal poverty line, or about $15,900 for an individual, would qualify for expanded Medicaid in North Carolina.

Arkansas: The promise of a "private option" in Medicaid
Sen. Mark Pryor (D) vs. Rep. Tom Cotton (R)

Arkansas has been one of the most interesting states to watch on Obamacare implementation. A popular conservative Democratic governor working with a new Republican majority in the state legislature last year came together to extend coverage to the Medicaid expansion population through the use of private health plans. This Medicaid "private option," as it's known, is being copied or studied in other conservative states.

As my colleague Greg Sargent recently reported, Pryor won’t “shy away” from making the case for the private option, which has enrolled more than 150,000 low-income residents.

The Arkansas Medicaid expansion plan narrowly survived a legislative defunding effort earlier this year, and voters in this week’s state legislative primaries sent “mixed signals” about their feelings on the plan. The Associated Press pointed out that one state lawmaker supporting the program lost the primary, another supporter won, and a chief Republican architect of the plan faces a run-off election in June.

The Medicaid expansion did poll pretty well in Arkansas earlier in the year – as long as it wasn’t connected to the health-care law. In one January poll, 47.5 percent said the private option should continue, while 32.5 percent said it should be canned. But when the issue was tied directly to Obamacare, just 35 percent supported and 39 percent opposed it.