Late last year, vulnerable Democratic candidates worried that deep problems with the health care law could sink their chances of keeping a majority in the Senate.

Now, suddenly, one red-state Democrat is praising the law in a new television ad — an indicator that public opinion of health care reform might have turned a corner.

In the ad, Sen. Mark Pryor and his father, former Sen. David Pryor, recount Mark Pryor's own bout with cancer and his struggle finding health insurance that would cover it.

"Mark's insurance company didn't want to pay for the treatment that ultimately saved his life," David Pryor says in the ad.

"No one should be fighting for an insurance company while you're fighting for your life," Mark Pryor adds. "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."

Pryor does not explicitly refer to the law by its common names, Obamacare or the Affordable Care Act, in the ad. According to the Washington Post, Pryor's campaign will spend six figures to air the new ad.

Polls have consistently shown that, even at times when most Americans opposed the health care law, most people at the same time supported many of its individual provisions, including the ones Pryor singles out in his ad.

But Democrats have shown a mixed record highlighting those popular aspects of the law so far this election cycle — particularly during the rockiest periods of the health care rollout late last year, when most vulnerable Democratic candidates did their best to change the subject from health care entirely.

As Democrats have grappled with how best to talk about health care, few have made it the subject of positive advertising.

In one exceptional case, Put Alaska First, a group funded by the pro-Democratic Senate Majority PAC to fund Sen. Mark Begich, D-Alaska, released an ad in April with a similar narrative arc to Pryor's new ad.

"I was lucky. I beat cancer," an Alaska woman, Lisa Keller, said in the ad. "But the insurance companies still denied me health insurance, just because of a pre-existing condition. I now have health insurance again because of Mark Begich."

But Pryor's ad, produced directly by his campaign, marks a slightly more significant turn in the 2014 midterm election cycle — and hints that Democrats might not avoid health care reform as much as, only a few months ago, it seemed they might.