A group of Democratic senators on Wednesday introduced an expanded public option for health insurance as the party debates the next steps to build on ObamaCare.

The new proposal, called the Choose Medicare Act, was introduced by Sens. Chris Murphy (D-Conn.) and Jeff Merkley (D-Ore.), both seen as potential presidential contenders, though Murphy has said he is not running in 2020.

The measure has no real chance of becoming law anytime soon, but is part of a growing debate among Democrats about what the best next steps beyond ObamaCare are, which could come to fruition when Democrats next win back the White House.

The bill takes a less sweeping approach than the "Medicare for all" plan championed by Sen. Bernie Sanders (I-Vt.). It preserves private insurance while allowing people in ObamaCare plans and employers to choose the new Medicare-based insurance plan if they want.

Merkley is also a supporter of Sanders's bill, while Murphy is not. Murphy said he thinks it is good that Democrats are throwing out different ideas to be considered.

"There are some Democrats that have proposed legislation mandating that all Americans move to a Medicare plan under the theory that Medicare is the best option available for Americans," Murphy said.

"Our bill essentially puts this theory to the test and lets consumers and businesses decide whether they want to migrate to a Medicare plan or whether they want to stay on private insurance," he added.

Merkley noted that he and Murphy have differing views on Medicare for all, but said this bill is a "a common vision that both perspectives can buy into" in the interim.

Sens. Kamala Harris (D-Calif.) and Cory Booker (D-N.J.), both seen as leading potential presidential contenders, are also co-sponsoring the Murphy-Merkley bill, in addition to backing Sanders's bill.

Other cosponsors include Sens. Tammy Baldwin (D-Wis.), Brian Schatz (D-Hawaii), Jeanne Shaheen (D-N.H.), Richard Blumenthal (D-Conn.), Martin Heinrich (D-N.M.) and Tom Udall (D-N.M.).

The bill, in addition to providing a public option, also boosts the generosity of ObamaCare's subsidies to help make insurance more affordable, and makes people at higher income levels eligible for the assistance.