It’s 2020, the Iowa caucus is weeks away and California’s March 3 presidential primary is just around the corner. Health care reform continues to be a major topic in the Democratic presidential primary race, with eight out of 10 likely Democratic primary voters in California saying health care is a top priority, according to a recent University of California-Berkeley Institute of Governmental Studies poll.

But, perhaps surprisingly, 57 percent of the state’s likely Democratic primary voters tell Berkley IGS that they favor incrementally changing the existing private health care system while just 37 percent want to replace the private system with a single-payer Medicare for All system.

Many of the leading Democratic candidates, including Sens. Bernie Sanders and Elizabeth Warren, have pushed the less popular Medicare for All approach, which comes with serious risks for those in need of timely health care.

Although Medicare for All means different things to different people, the most relevant definition is the text of S.1129, the Medicare for All Act proposed by Sanders and co-sponsored by fellow presidential candidates Warren and Sen. Cory Booker. Their bill forbids all forms of patient cost-sharing for medical services. In other words, anyone would be able to see a doctor or obtain hospital treatments without making copayments or paying deductibles. This is wonderful in theory but raises major practical problems.

Co-payments and deductibles restrain the demand for medical services.  Medicare for All advocates argue coinsurance deters patients from seeking necessary care, but not all care is necessary. Physicians surveyed by a team of researchers in 2014 reported that about 20 percent of medical care was unnecessary, “including 22 percent of prescription medications, 24.9 percent of tests, and 11.1 percent of procedures.”

And that’s under our current system. Without co-payments or deductibles, more patients who might otherwise deal with minor medical complaints at home or with over-the-counter medicines would instead likely head to the doctor.

The Medicare for All bill also effectively eliminates provider networks, allowing anyone to receive care from any physician at any medical facility. Thus, with coinsurance and provider network limitations abolished, demand for medical services would grow but it’s not at all clear there would be a greater supply of health care ready to meet that demand.

Although Section 613 of Sen. Sanders’ bill speaks in broad terms about expanding the number of providers, it offers no specific policies for doing so.  In fact, the legislation could encourage physician retirements because it limits the reimbursement rates doctors could receive for their work.

The bill would likely produce a shortage of medical care services and increased wait times. This type of queue is common in countries with government-dominated health care systems. In the United Kingdom, for example, the National Health Service has a target of 62 days between a general practitioner referral for cancer care and the initiation of treatment, but this target is only met 80 percent of the time. In Canada, the median wait time from a general practitioner referral for orthopedic surgery is 39 weeks, which is perhaps why 63,000 Canadians went abroad for procedures in 2016, according to the Fraser Institute.

In the United States, we have already seen similar problems with the Veterans Health Administration (VA). This federally-controlled health care system appeared, from afar, to be operating tolerably until a scandal emerged at the Phoenix Veteran’s Administration hospital in 2014. The facility reported there was a 24-day wait time for an initial appointment with a general practitioner but it was maintaining a secret waiting list and the actual wait time was 115 days. Dozens of patients died while waiting for appointments.

Across the country, the VA continues to struggle with accurate wait time reporting and some patients are still waiting up to 70 days to see a doctor.

It’s clear that Medicare for All would ration care and create long waits for many patients.  The majority of likely California Democratic primary voters who told Berkeley IGS they prefer modifying the existing private health care system over Medicare for All have it right. Hopefully, the party’s presidential candidates are listening.

This column originally appeared in the Orange County Register.