On the surface, Sen. Mark Pryor's latest ad is almost unremarkable.

Released this week, the ad starts with the embattled Arkansas incumbent sitting at a table with his father David, a former senator, as the two recount his battle with cancer.

But it then does something few Democratic campaigns have dared in the last four years: Defend Obamacare.

"No one should be fighting for an insurance company while you're fighting for your life," Pryor says in the ad. "That's why I helped pass a law that prevents insurance companies from canceling your policy if you get sick, or deny coverage for pre-existing conditions."

The straight-to-camera endorsement of major Obamacare provisions by a vulnerable, red-state Democrat seems to mark an extraordinary shift after several election cycles that have been colored by poor public opinion of the healthcare law.

Or does it?

“This was not about endorsing ACA,” Justin Barasky, spokesman for the Democratic Senatorial Campaign Committee, told PBS. “If it was, [Pryor] would have mentioned it by name.”

“The ad features Mark's father,” Barasky later told the Washington Examiner, “and it's about Mark Pryor telling his personal story about cancer and fighting the insurance companies.”

But the ad could have an important, added benefit, one that has so far eluded many vulnerable Democrats: helping Pryor fight back against Republican attacks on the health care law, which have been fierce and frequent. Pryor’s focus on fighting insurance companies in particular offers a peek into how other Democrats could defend against health care attacks moving forward.

“This ad is little more than an attempt to inoculate a very vulnerable Senator from a law that is extremely unpopular in his state,” wrote Brad Dayspring, a spokesperson for the National Republican Senatorial Committee.

After the bungled rollout of the Affordable Care Act's online insurance exchange last fall, Democrats panicked that it would help renew criticism of the law that led to GOP success in the 2010 midterms. Instead, the issue has settled into a political equilibrium, with both sides claiming partial victories.

Republicans and their allied outside groups have spent millions of dollars sullying the term “Obamacare” in voters’ minds by highlighting health care costs and people whose insurance has been canceled.

And Democrats have stressed that many of the individual provisions in the health care law, including those highlighted by Pryor in his ad, remain popular with the majority of Americans.

That doesn’t mean Obamacare is any easier to talk about. Even as Democrats such as Pryor rattle off its selling points, Obamacare is still the law that shall not be named. Republicans were quick to point out that in Pryor’s ad, he didn’t say “Obamacare” or “Affordable Care Act” once.

The same dynamic played out in an ad that aired earlier this year in Alaska. The TV spot, which was funded by Put Alaska First, a group supporting Democratic Sen. Mark Begich, featured a cancer survivor who credited Begich with fighting health insurance companies to help her keep her coverage. Not credited: the president’s health care law.

But just as the issue is no longer not the certain hazard it once was for Democrats, nor is it a political panacea for Republicans.

The number of ads attacking Obamacare, Bloomberg noted this week, has been cut in half from April, hinting at a shift in focus from health care to other issues, such as immigration.

Part of the decrease also comes because Americans for Prosperity, a major Republican outside group, has for the time being shifted gears from its relentless focus on the subject. Some Republicans say Americans have heard enough about Obamacare, but that it will nevertheless be a prominent issue in the midterm elections.

“Obamacare is one of those rare political issues that is already a baked-in, hard negative for Democrats across the country and particularly among the millions of Americans who lost their health care plans because of it,” said Brian Walsh, a former NRSC spokesperson who still advises the committee. “So it certainly doesn't surprise me if more Republicans campaigns expand their messaging to other issue areas of Democratic mismanagement and incompetence.”

Having a broader message might be especially important to Republicans with certain health care variables yet undefined. Rates of uninsured have decreased in most parts of the country this year as the health care law has been implemented and, in particular, as some states have expanded Medicaid.

Some of the key Senate battleground states have seen the greatest change. In Arkansas, which ranks No. 1, the percentage of uninsured has dropped 10 percent since last year, according to Gallup.

Said one Democratic strategist, “It’s harder for Republicans to stand up and talk about repeal when they’d be taking insurance away from thousands of people.”