The bill, which proposes establishing a health care trust that would be responsible for collecting and disbursing funds needed to provide health care services for Commonwealth residents, would be funded through a 10 percent payroll tax — 7.5 percent for employers and 2.5 percent for employees — and a tax of 12.5 percent on unearned income.

Ms. London, who was involved in the fiscal analysis of Vermont’s failed single-payer effort, said the 10 percent payroll tax struck her as low.

“Moving from a privately financed system to a publicly financed system is incredibly complex,” she said, adding if Massachusetts truly wants to move towards single-payer, an incremental approach would be better. She suggested creating a public plan and giving residents the option to choose it.

“If you build something people really like, they will move into it. Then you can start to phase out some of the private,” she said. “If it’s lower cost and better quality, people will choose it.”

State Sen. Anne M. Gobi, D-Spencer, one of the co-sponsors of Sen. Eldridge’s bill, acknowledged the complexity of setting up a government-financed health care system.

“Change is always very difficult,” she acknowledged. “This is a totally different way of looking at how health care would be delivered. It would require drastic overhauls.”

However, she said she thought the time was ripe to have a serious discussion about implementing single-payer.

“There’s a lot of uncertainty in Massachusetts with what’s happening on the federal level,” she said, referring to the Republican plan to overhaul the current health care law.

“I do think the timing is right,” she said, “to at least have for a very serious conversation on this and to look at how this could be implemented.”