Former Vice President Joe Biden, in the first rally of his 2020 presidential campaign, said "we have to finish the job" by expanding Obamacare to include a new government-run plan, which was originally pushed by President Barack Obama, before the idea fell short of votes in the Senate.

In doing so, Biden was breaking with many of his rivals on the healthcare issue, who want to replace all private insurance and put everybody on a single government-run plan under the banner of "Medicare for all."

"Affordable healthcare was a huge step forward, the ACA, in our country," Biden said in touting Obamacare. "We made historic progress by extending healthcare to 22 million people ... We have to stop this administration's effort to gut it first, then we have to move on and finish the job and make healthcare a right."

Echoing his rival Sen. Bernie Sanders, I-Vt., Biden said "Healthcare's a right, not a privilege." But unlike Sanders, who has proposed transitioning all Americans into one government plan and outlawing private insurance that would attempt to offer similar benefits, Biden is arguing for making such a plan optional.

"We have to give everybody the peace of mind they deserve," Biden said. "Whether you're covering it through your employer, or on your own, or not, you all should have your choice to be able to buy into a public option plan from Medicare. Your choice."

Back in 2009, the idea of the so-called public option went down in flames as more centrist Democrats opposed it under criticism that it was a Trojan horse for a fully government-run system. Though pitched as a choice, the problem is that government would be setting the rules of the game, meaning that it could rig things in a way that steers more Americans toward the government plan, allowing the American system to transition to a socialized health insurance system over time.

Since the Obama years, many Democrats have moved away from supporting an incremental step, and, inspired by Sanders, have embraced the socialized model directly. The Sanders bill itself was co-sponsored by 2020 rivals Sens. Cory Booker, D-N.J., Kirsten Gillibrand, D-N.Y., Kamala Harris, D-Calif., and Elizabeth Warren, D-Mass.

The Biden position on healthcare will tee up what is expected to be one of the core philosophical battles of the Democratic primary. Do voters want to essentially pick up where Obama left off and build on his legacy? Or do they want to go in an even more aggressive direction to radically transform America?