U.S. Sens. Michael Bennet of Colorado and Tim Kaine of Virginia, both Democrats, on Tuesday introduced legislation to create a government-run health insurance plan that would eventually allow anyone to buy coverage under Medicare, the federal program that covers the elderly.

“This bill creates a true public option, which I believe we should have passed with the Affordable Care Act,” Bennet said in a call with reporters.

The plan, called “Medicare-X,” would be available initially in areas that lack competition – including 14 mostly rural counties in Colorado with only one insurance option – and would roll out nationwide by 2023. Participants could qualify for the same tax credits and cost-sharing reduction payments available under the Affordable Care Act, known as Obamacare.

“There was no reason to reinvent the wheel,” Bennet said. “The plan uses exactly the same network that’s open to Medicare patients today. At least the network is set up on Day One.”

Although it wouldn’t involve paying into the existing Medicare trust fund, participants would be able to use Medicare’s network of doctors operating under already-set reimbursement rates. The plan would guarantee coverage of Obamacare-mandated essential health benefits, including maternity care and mental health. The bill would also allow the federal government to negotiate the plan’s prescription drug prices along with the Medicare Part D program.

“We’re in a moment still where people want to re-litigate, once again, the Affordable Care Act after trying to repeal it almost 70 times,” Bennet said, adding, “This is a perfect moment for us to work in a bipartisan way to improve not just the Affordable Care Act but the American health care system.”

The legislation’s chances in the GOP-controlled Senate could be dim. While Bennet said he hopes Republican senators will find the proposal attractive “because it adds a choice for people,” the bill’s sponsors have yet to find a Republican willing to sign on. That, Bennet mused, could be due to “residual concern about being painted as someone who’s trying to fix rather than sabotage the Affordable Care Act.”

The Medicare-X plan differs from the so-called single-payer legislation sponsored by Vermont Sen. Bernie Sanders and dubbed “Medicare for all,” which would replace existing health plans with a single national plan. About one-third of Democratic senators have signed on to support that approach.

The Bennet-Kaine bill would establish a system existing side-by-side with employer-based insurance, insurance policies sold on state and federal health care exchanges and the Medicare and Medicaid programs, Bennet stressed.

“As a country, one way or another, we need to reach a point where every American has affordable, reliable health insurance,” he said. “This bill is a step in that direction.”