But in the days since, it's become clear: there's little evidence that the hotly debated law is on its way to becoming a central Democratic talking point heading into the fall campaign.
"It’s basically the first pro-Obamacare ad we’ve seen by a vulnerable Democrat for months," said Elizabeth Wilner, senior vice president of Kantar Media Ad Intelligence, whose Campaign Media Analysis Group tracks political advertising. "It’s like seeing a unicorn – it just doesn’t happen very often."
Wilner also noted that the ad -- which featured Pryor sitting with his father, the well-liked former Sen. David Pryor -- only obliquely referred to the Affordable Care Act. It focused instead on how Mark Pryor wrangled with his insurance company when he battled cancer 20 years ago.
Indeed, party strategists cast the commercial as a bio spot -- one that served to remind voters of Pryor’s personal history.
"It is a powerful, personal story about Mark and his family’s fight with the insurance companies, and what Mark did as senator to make sure other Arkansans don’t have to go through that," said Matt Canter, spokesman for the Democratic Senatorial Campaign Committee.
While liberal supporters believe Obamacare could be a winning issue for Democrats, recent polls show that the law continues to be unpopular. A CBS poll taken in early August found that 50 percent disapprove of the measure, while 41 percent approve. Strong disapproval outpaced strong approval by a nearly 2 to 1 margin (38 to 20 percent).
When they have brought up Obamacare on the campaign trail, Democrats have argued that Republicans would roll back popular aspects of the law, such as the ban on denying people coverage for preexisting conditions.
"Yes, there is a line of attack that can be used, but by and large, most candidates do not want to be in a situation of running their race on Obamacare," said one Democratic strategist who requested anonymity to discuss internal strategy. "It’s still unpopular, and it’s not going to be popular by the time the election comes around."
Even in a state like Kentucky, where the state-based insurance exchange is viewed as a success story, Democratic Senate challenger Alison Lundergan Grimes has not made the law a centerpiece of her campaign against Minority Leader Mitch McConnell (R).
In fact, she made news last week by offering rare praise for the benefits of the law at a Farm Bureau Federation forum in Louisville, casting it as a victory for state control.
"Mitch McConnell, if he had his way, he'd cede all the power to the federal government," Grimes said. "I choose Kentucky, the 500,000 individuals who for the first time ever have access to insurance."
"She won't use the words, but she supports Obamacare," McConnell responded.
Republicans and their outside allies are still pressing a harsh critique of President Obama’s signature legislation; 19 new anti-Obamacare spots went up around the country last week, Wilner said. But they are also expanding their arsenal with other messages heading into the fall.
That’s in part because the health-care fight has not been the overriding issue of this year’s midterms in the way that many predicted it would be. Instead, voters have been preoccupied with a slew of concerns including jobs, the minimum wage, government spending, immigration and foreign entanglements.
"It’s still a top issue, but it’s no longer the top issue," Wilner said, adding: "It was unrealistic to expect it to remain the number one issue. The problems with enrollment are over. So it’s a more diffused message than before."
Scott Clement contributed to this report.