Sen. Bill Cassidy (R-La.) testifies alongside former senator Rick Santorum during a Senate Committee on Finance hearing on Monday. (AFP/Getty Images)

Halfway through CNN’s prime-time debate on the Affordable Care Act, Sen. Bernie Sanders (I-Vt.) went in for the kill. Sen. Lindsey O. Graham (R-S.C.) had taken his umpteenth swing at “bureaucrats,” telling viewers that “Bernie’s solution is more government, not less,” warning that the Vermont senator would pour millions of people into Medicare when the system could not handle them.

“It is easy to beat up on big, bad federal government,” Sanders said. “Guys, do you know what the most popular health insurance program in America is? It’s not the private insurance industry. It is …”

Graham decided not to dodge.

“Medicare,” he said.

“Medicare, yeah!” Sanders said.

“Which is falling apart,” Graham said.

It was a particularly telling moment in CNN’s 90-minute special, one that pitted Graham and Sen. Bill Cassidy (R-La.), the main sponsors of a faltering Affordable Care Act repeal bill, against Sanders and center-left Sen. Amy Klobuchar (D-Minn.). When the debate was announced, the Cassidy-Graham bill looked very much alive; some Democratic pundits asked whether Sanders had given the Republicans the black-and-white contrast, “single payer” versus Medicaid reform, that they had craved.

With support growing for universal health coverage, just what does "single-payer" mean? Here's a deep-dive into what a single-payer health-care system would look like, and the arguments for and against it. (Jenny Starrs,Danielle Kunitz/The Washington Post)

But by 9 p.m. Eastern, when the debate began, Cassidy-Graham was headed for the ash heap. “It’s okay to fall short,” Graham said near the start of the debate, all but conceding defeat. The reality on the Hill had turned the debate into a lower-stakes argument about the best way to deliver health care.

The four senators represented three approaches, with Klobuchar — one of 31 Senate Democrats who declined to co-sponsor Sanders’s health-care bill — arguing for a return to bipartisanship. A Republican mention of Cassidy-Graham support from governors would earn a Klobuchar reference to “the independent governor of Alaska” or “the governor of Ohio,” both opponents of the bill.

“When you hear that there’s only two choices here — that’s not true! There is another choice,” Klobuchar said.

Klobuchar and Sanders stayed united to rip apart Cassidy-Graham, quoting from Congressional Budget Office studies and medical industry statements to portray the Republican bill as radical and unworkable.

“It’s not giving people a choice. It’s cutting Medicare by a trillion dollars,” Sanders said.

Cassidy and Graham, both of whom had defended their bill in the Senate Finance Committee, stuck to their workshopped arguments.

“I want to take care of you and your daughter, but I want to do it in a way not to kick everybody into a situation where insurance really doesn’t mean a lot,” Graham said to one audience member who worried about his family’s care. “The guy in Obamacare who’s deciding adequate and affordable is doing a miserable job, or I wouldn’t be here.”

Senate Republicans are trying to revive the momentum to overhaul the Affordable Care Act with the Cassidy-Graham proposal. Here are five things to know about the plan and the rush to pass it. (Jenny Starrs/The Washington Post)

Cassidy, a medical doctor who repeatedly pointed to his experience in the field, made more specific arguments for the bill. Unbowed by the negative ratings from the CBO — which found that it would cut the deficit at the cost of uninsuring millions — he repeatedly invoked the “long arm of Washington,” warning that any bill that did not devolve power to states would enable extremism.

But it was Graham and Sanders, a combined 50 years on the Hill between them, who bantered the most. At one point, Graham rattled off the growing stock prices of the largest health-care companies. Sanders smiled widely.

“You actually said something that was right! I knew it would happen,” he said. “This system is designed to make money for insurance companies. Our money should be going to doctors, nurses and hospitals.”