America isn’t ready for “Medicare for All.” Fortunately, Democratic candidates for president are starting to get it.

On the immigration front, America isn’t ready to decriminalize illegal border crossings. Democratic candidates need to get a grip on that, too, if they want to beat President Donald Trump in 2020.

Democrat Harry Reid, a former U.S. Senate majority leader, nailed it when addressing both topics in an interview with VICE News.

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Asked if support for Medicare for All would be problematic in next year’s general election, Reid said, “of course it would be,” in an article published Tuesday.

Democrats won big in the 2018 midterms in part by standing up for the Affordable Care Act amid attempts by Trump and the Republican Party to get rid of Obamacare. The GOP is still trying to get rid of it through the courts.

Dems should stick with Obamacare, as Reid advised. Focus on improving it. Don’t venture too far into left field, on health insurance and other issues. That’s a surefire way to smooth Trump’s path to re-election.

Reid told VICE that Dems should focus on improving Obamacare “without bringing something that would be much harder to sell.”

Medicare for All and universal health care coverage are a much tougher sell because many Americans, including many in the middle class, have solid plans through private insurance that they get through employers. They don’t want to give them up.

A tracking poll in July by the Kaiser Family Foundation, a nonpartisan nonprofit, found that 55 percent of Democrats and Democratic-leaning independents prefer that health care coverage be expanded by building on Obamacare, compared to 39 percent who prefer Medicare for All.

Joe Biden gets it. The former vice president’s plan is to keep Obamacare and add a public health insurance option, “like Medicare,” he says on his website.

Presidential candidate Kamala Harris, a senator from California, is coming around to that more mainstream view and is backing away from a Medicare for All plan. She and former U.S. Rep. Beto O’Rourke now want to keep employer-based plans.

On immigration, Democratic candidates Julián Castro, a former housing secretary under President Barack Obama, Sen. Elizabeth Warren and Mayor Pete Buttigieg of South Bend, Indiana, earlier this summer said illegal border crossings should no longer be criminal offenses.

The law says such crossings are misdemeanor offenses, punishable by a fine and up to six months in prison. It was enacted in the 1920s at a time when Congress wanted to curtail Mexican immigration in favor of immigration by whites.

Typically, however, immigrants caught crossing illegally have ended up in civil proceedings rather than criminal ones. Prosecuting people at times picked up steam under Presidents George W. Bush, Obama and now Trump.

Castro is eloquent on this topic, pointing out that Trump has “weaponized” the law to try to make crimes out of asylum claims made outside ports of entry.

But most of America isn’t up to speed on this. On the whole, we’re not ready.

“There are so many more important things to do,” Reid told VICE. “Decriminalizing border crossings is not something that should be at the top of the list. It should be way, way down at the bottom of the list.”

Reid’s right again. Stick with pushing for a fair immigration system. That will resonate with a majority of Americans. Promise to treat migrant children humanely as Trump attempts to criminalize and jail them indefinitely.

Castro has a lot of good ideas on immigration. But with immigration, as with health care, if you want to do too much too soon, it will sink you.

Marlen Garcia is a member of the Sun-Times Editorial Board.