People rally in favor of single-payer health care outside of the office of Speaker of the California State Assembly Anthony Rendon on June 27th, 2017, in South Gate, California. (Photo: Robyn Beck/AFP/Getty Images)

The health-care debate in Washington, D.C., has swallowed the first six months of President Donald Trump's legislative agenda, with a seemingly endless list of efforts to repeal the Affordable Care Act cropping up—and falling short—every few weeks.

The issue has also burned hot in California this year, where support for single-payer health care is fast becoming a litmus test for Democrats. The political battle over health care has emerged among the party's base as one of the most important early issues in the 2018 governor's race, and Democrats' success in finding a message that reaches swing voters could be pivotal in the half-dozen potentially competitive congressional races in the state next fall. Those races, in turn, may determine partisan control of the House—and the future of the Trump presidency.

When it comes to health care, the stakes are as high as the politics are fraught. California State Assembly Speaker Anthony Rendon shelved a single-payer proposal that was passed by the more liberal state Senate earlier this year. That maneuver earned Rendon the rebuke of the left wing of the Democratic Party and made him a a target of a recall election brought by members of his own party.

With the debate over the future of health care becoming more important in California, Rendon has called a series of hearings to help take stock of where California stands, and to help chart a path forward.

"There are several different approaches being proposed, including Medicare for all, single payer, hybrid systems, and ACA expansion," Rendon said in a statement announcing the hearings. "I have called for these hearings to determine what approach best gets us there—what gets us to 'yes' when it comes to health care for all."

The fight for the heart and soul of the Democratic Party is well underway, and the future of health care figures to play front and center.

Among the ideas to be discussed is a potential amalgam of the private insurance-based model of the Affordable Care Act and the government-driven model of single payer. This hybrid would expand single-payer coverage to those 55 and older, while trying to shore up the private insurance market for children and younger adults.

The idea is already the preferred approach of a number of Democrats from pivotal swing states. Senators including Sherrod Brown (D-Ohio), Debbie Stabenow (D-Michigan), Tammy Baldwin (D-Wisconsin), and Al Franken (D-Minnesota) have all supported the Medicare at 55 Act. The proposal, which was introduced earlier this year, would move millions of Americans into the single-payer world of Medicare, while potentially making it more appealing for private insurers to offer coverage to children and younger adults.

"People in the 55-64 age group face unique health challenges and especially high health-care costs," reads a statement issued by Brown's office. "The average person in this age group pays more than $1,200 in annual out-of-pocket costs and is at a greater risk of suffering from chronic conditions such as diabetes or arthritis and medical emergencies such as heart attack and stroke."

Moving those expensive patients into Medicare could help control costs for private insurance companies and, the thinking goes, lower the cost of private premiums.

In states like California that have fully embraced the state-run private exchange and Medicaid expansion pieces of the Affordable Care Act, Brown's proposal would transfer some of the financial burden from states to the federal government, while seeking to make the exchange more appealing to insurers, and more affordable for customers.

That approach falls short of the Medicare for All idea embraced by Senator Bernie Sanders (I-Vermont) and backed by freshman California Senator Kamala Harris, but could be seen as a step in the direction toward single payer. Whether the proposal is politically tenable—either to the party's base, or to the political center—remains to be seen.

What is made clear is that the fight for the heart and soul of the Democratic Party is well underway, and the future of health care figures to play front and center—not surprising, given the sector accounts for nearly 18 percent of the nation's total economic activity, and provides a service for which the average American pays more than $10,000 annually.

As Democrats try to find a message and set of policies that will unite the base and resonate with a broader, national audience, the skirmish under way in Sacramento may yet prove to be a political lesson that will have national implications, and determine whether Democrats can find common ground—and articulate a clear message—on a fundamental political issue.