There’s another side to the story—if only Pryor wanted to tell it. In Arkansas, roughly 103,000 people without health insurance now have it, thanks to Obamacare. Yet Pryor’s response this week to attacks on the health care law was a television ad assailing his GOP rival’s position on Medicare, not Obamacare. “[Tom] Cotton voted in Congress to change Medicare into a voucher system that will increase out-of-pocket expenses for every senior in Arkansas,” says the woman named “Courtney” in the ad.

Democrats’ decision not to fight fire with fire is strategic: If they’re arguing about the divisive and disruptive overhaul of the nation’s health care system, they’re already losing. That’s even more true in the wake of a new Congressional Budget Office report that estimates the law would encourage about 2 million employees to leave the workforce.

“You don’t want the election to be about Obamacare,” conceded Neera Tanden, president of the liberal Center for American Progress, which in the past has urged the White House to more aggressively sell the health care law.

The reluctance to defend the health care law is not for lack of success stories. Roughly 4 million people have signed up for private insurance or qualified for Medicaid under Obamacare. Organizing for Action features dozens of satisfied customers on the “This is Why” section of its website.