In a crowded field of Democrats vying for the presidency in 2020, one thing stands out. “Medicare for All” tops the party’s agenda. On Tuesday, Sen. Kirsten Gillibrand threw her hat in the ring, ­becoming the latest announced candidate pledging to make universal health care a reality.

But these candidates would rather walk on hot coals than tell you what Medicare for All costs: a whopping $32 trillion over 10 years. To raise that, all taxpayers, not just the rich, would have to hand a gut-wrenching share of their paychecks to Uncle Sam, based on Congressional Budget Office revenue tables.

A single guy earning $82,500 a year, and currently paying a 24 percent marginal rate, would be hit with a 60 percent tax rate ­instead. A couple reporting $165,000 in income would also see their marginal rate soar to 60 percent from 24 percent. No more dinners out or family trips. Goodbye to your standard of living.

And to America’s current medical standard of care. Liberals want to keep the name Medicare but change everything else. The result will be stingy care for all.

Here’s why.

Today, Medicare pays doctors and hospitals about 87 cents for every dollar’s worth of care, ­according to the American Hospital Association. Why do doctors and hospitals go along with the shortchanging? Because they can shift their unmet cost onto younger, privately insured patients.

But Medicare for All outlaws private insurance. All patients will be underpaying, leaving hospitals with less money. “Many hospitals wouldn’t be able to keep their doors open,” says Chip Kahn of the Federation of American Hospitals. Those that do will be jamming more beds in a room and making patients wait longer for a nurse.

That could be you. If you have insurance now, you won’t be ­allowed to keep it. Nationwide, 156 million people who get coverage through a job will be forced to give it up.

Employers and unions are barred from covering workers or their families. Public unions are already protesting. The gainfully employed will end up subsidizing a huge entitlement, and get nothing more than what someone who refuses to work gets. What’s the ­incentive to work or join a union?

Instead of facts, Democrats are offering happy talk. Last week, Mayor Bill de Blasio boasted that “from this moment on in New York City, everyone is guaranteed the right to health care.” Not just emergency room visits but a primary care physician.

De Blasio put the cost of covering 600,000 uninsured people at $100 million a year and said no tax hikes are needed. That miracle math works out to $170 per person. In truth, it won’t pay for one doctor’s visit, much less tests or drugs.

But this urban Robin Hood knows he will need more. In his State of the City Address, he said, “Brothers and sisters, there’s plenty of money in the world, plenty of money in this city. It’s just in the wrong hands.”

Meaning the hands of the people who earned it.

Vermont socialist Sen. Bernie Sanders’ approach is only slightly less confiscatory. There is no disputing the $32 trillion cost of Medicare for All — a number on which the left-leaning Urban Institute and the right-leaning Mercatus Center at George Mason University agree. Sanders proposed hiking the capital-gains tax rate as much as ­64.2 percent to pay for it.

That would torpedo economic growth. He also proposed an unprecedented tax on wealth. Even these radical ploys would raise less than half of the cost, according to the Tax Policy Center.

The larger question here is whether the Democrats are the party of capitalism — or confiscation. Some Dems are pledging to soak the rich, and others are catering to them. Westchester Democrat Rep. Nita Lowey is pushing to restore full federal deductibility of state and local taxes, benefitting her well-heeled constituents.

In the midterms, Democrats swept the 10 richest congressional districts in the nation. In other words, they are becoming the party of the ultra-rich and the very poor. Medicare for All offers nothing for the vast middle — working people.

That’s a huge opportunity for Republicans. They need to offer practical fixes for the unaffordable deductibles and suffocating paperwork that make people angry. And they need to remind voters that massive tax hikes to pay for single-payer health care will destroy economic growth, robbing all of us, rich, poor and middle class alike.

Betsy McCaughey is a former lieutenant governor of New York.