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BOSTON — Lawmakers proposing that Massachusetts adopt a single-payer health care system were grilled Tuesday by one of their powerful Democratic colleagues, who said she’s a “big believer in single-payer health care” but that moving from theoretical support to implementation becomes “dicey.”

The complexity is not as simple as the tagline ‘Medicare for all’ for us,” Health Care Financing Committee Co-chair Rep. Jennifer Benson told sponsors of single-payer legislation at a hearing on their bills.

“The federal government needs to expand Medicare, period. That is the right solution that could be done easy, so to speak, but we have to create an entire new system and answer those questions on our own.”

Sen. Jamie Eldridge, Rep. Lindsay Sabadosa and Rep. Denise Garlick have filed bills (H 1194, S 683) that would establish a government-run single-payer or “Medicare for all” system to provide health care to all Massachusetts residents, funded through a payroll tax.

With nine other lawmakers behind them, they told personal stories about challenges accessing care and said single-payer would make health care more equitable, simplify the system, and provide better access to treatment for addiction treatment, reproductive health and mental health services.

After they wrapped up, Benson and other committee members peppered them with questions on issues including costs, implementation timeline and details, the handling of out-of-state residents who work in Massachusetts, when and whether the state would be able to get a Medicaid waiver from the federal government, and what happens if a Massachusetts resident needs extensive medical care in another state.

Sen. Cindy Friedman, the committee’s Senate chair, said the panel needed answers to those questions to “bring the public along with us” through honesty about what single-payer would look like and the trade-offs involved.

Drawing a chorus of approving finger-snaps from the crowd, Eldridge said supporters of the bill are arguing for a “totally revolutionary system” because “playing around the edges is not going to address costs.”

In response to a question about costs from Rep. Steve Ultrino, Eldridge said studies have indicated the payroll tax would be less expensive than costs associated with the current system, including copays, deductibles and premiums.

Eldridge, an Acton Democrat, said he suffered a major seizure 10 years ago and spent six weeks in the hospital and a rehabilitation center.

It took him three years to pay off his medical bills, he said.

“That really shows how broken this health care system is,” he said.