Medicare for All has emerged as a defining issue in the race for the White House. Several contenders for the Democratic nomination for president support expanding Medicare to cover all Americans.

But the idea may not play well with the public. Medicare for All would take away existing health insurance coverage from tens of millions of Americans -- and deprive them of any say over their health care. In exchange for sacrificing control of their health care, Americans would pay trillions of dollars in new taxes.

Consider Sen. Bernie Sanders’ Medicare for All Act, which would enroll all Americans in a new government-run health plan.

No one would have a choice. The bill would outlaw private insurance coverage. More than 150 million people with employer-sponsored insurance plans, 20 million people who purchase coverage on the individual market, and 20 million people with privately administered Medicare Advantage plans would find themselves in a one-size-fits-all government plan.

Experts peg the cost of Medicare for All at roughly $32 trillion over its first decade. Even doubling what the federal government takes in corporate and individual income tax would be insufficient to cover that tab.

The massive tax hikes needed to come up with that cash are deeply unpopular. Six in 10 Americans oppose Medicare for All once they learn it’ll require tax increases.

And that initial $32 trillion estimate may be low. The bill envisions paying healthcare providers at Medicare’s existing rates, which are 40 percent lower, on average, than those for private insurance.

Doctors and hospitals can’t simply absorb those kinds of pay cuts. Many healthcare facilities, especially those in rural areas, will close their doors. Physicians may retire early, cut the number of hours they work, or leave medicine altogether.

The result will be a healthcare system where everyone has coverage -- but no access to care.

That’s exactly how things work at the government-run Veterans Health Administration.

According to a 2017 audit of 12 VA facilities in North Carolina and Virginia conducted by the agency’s inspector general, one-third of veterans had to wait more than 30 days for a primary care appointment. The average wait for this group was 51 days. Thirty-nine percent of those waiting for an appointment for specialty care at the 12 hospitals and clinics idled for more than 30 days. The average wait for this group was 60 days.

Millions of Americans who have private health insurance have demonstrated they’re not interested in losing coverage for VA-style health care. Just look at the results of the recent midterm elections.

Seventy percent of Democrats that won Republican-held House seats – 21 out of 30 – do not support Medicare for All. Six of the seven Democrats who took state governorships from Republicans last fall also do not support the idea.

Meanwhile, two-thirds of Democrats who lost House seats to Republicans supported Medicare for All.

Ensuring everyone has access to health insurance is a laudable goal. But we can achieve it by building on what works in our current system and fixing what doesn’t. Seventy percent of those with employer-based plans are happy with their coverage. The nine-year-old Affordable Care Act has been gaining public support. A recent poll found 61 percent of Americans want the law to be retained or improved.

Medicare for All is not the only way to ensure universal access to health insurance. In fact, it’s the most expensive, most complicated, and most disruptive.

Janet Trautwein is CEO of the National Association of Health Underwriters (www.nahu.org