If Democrats capture the White House in 2020, the policies that created the disease-ridden tent slums taking over Los Angeles and San Francisco will start heading your way.

Presidential hopeful Liz Warren insists that it’s wrong to ban living on the streets and in public parks. Bernie Sanders is calling for a 3% cap on annual rent hikes, the kind of poisonous rent-control law that deters new housing construction and worsens homelessness.

As for Joe Biden, expect him to stick by the Obama administration’s policy that living on the street is a civil right. Never mind the harm street-dwellers inflict on the public’s health and safety and the suffering they ­endure themselves.

In downtown Los Angeles’ business district, many of the county’s 60,000 homeless live in tents and parked cars, defecating in buckets left on street corners for public sanitation workers to empty. Needles litter the sidewalks. Rats scamper by.

Murders are up 13% and rapes are up 61% in one year in these homeless camps. Typhus, a medieval disease carried by fleas, threatens not just the homeless but also cops on the beat there and anyone who walks by.

President Trump says “the people of Los Angeles are fed up.” The Washington Post bashes Trump for daring to “stigmatize” the homeless. ­Leftist advocates say complaining neighbors need “an immersion course” to increase their empathy.

Sorry. Trump’s right. What’s needed is an abrupt change from the delusional policies exacerbating homelessness.

Last week, Trump’s Council of Economic Advisors identified the biggest culprit: rent-control laws that discourage the real estate industry from building or refurbishing affordable spaces. Get rid of the regulations, and homelessness would fall 40% in Los Angeles and 54% in San Francisco.

Listen up, New York. The president’s report also estimates that abolishing rent regulations here would slash homelessness by 23%.

Tragically, New York Democrats — many of them rent-control ideologues — are propelling us in the opposite direction.

Gov. Andrew Cuomo just signed legislation that will block vacant apartments from being deregulated and make it harder for building owners to recoup repair costs or evict hellish tenants.

You can expect the housing crisis to worsen as a result.

Unlike California, in New York, shelter is a legal right, guaranteed by the courts. The city provides temporary housing for nearly all the homeless in shelters, apartments and even Holiday Inns. The cost to taxpayers is a whopping $2.14 billion a year.

New York subway riders, ­including kids going to school, also feel the brunt of homelessness. Vagrants defecate and sprawl out in the cars, making the ride gross.

What can a president do? Trump can’t change local and state laws, but federal departments such as Housing and Urban Development can offer incentives to eliminate over-regulation.

Sanders wants the opposite. Though rent control destroyed housing markets in New York and Los Angeles, he wants to spread it across the nation. Sanders’ plan is constitutionally dubious. Call it grandstanding. But even suggesting national rent control is damaging, because it will encourage more municipalities to adopt it.

Sanders and Warren would also spend hundreds of billions more on housing, falsely assuming that housing shortages are the only cause of homelessness. Democrats ignore the role of addiction and mental illness. As Trump’s report reminds us, de-institutionalization has been a disaster. “You can’t have all your faculties, if you’re living on the street,” says former NYC Police Commissioner Ray Kelly.

The Obama administration made homelessness worse by siding with vagrants when Boise, Idaho, tried to shut down its encampments. Obama’s Department of Justice called homelessness a lifestyle deserving ­legal protection. Preposterous, considering a homeless man can expect to survive only to age 47, and a homeless woman to 43, losing decades of life.

Yet the federal Ninth Circuit Court of Appeals ruled against Boise in 2018, so nine Western states are powerless to limit street living. Boise is appealing to the US Supreme Court.

Meanwhile, voters will have a choice in 2020. To surrender to the new Democratic normal of squalor and urban chaos or reclaim their neighborhoods, while humanely helping the homeless.

Betsy McCaughey is a former lieutenant governor of New York.