The Democratic Party is feeling the Bern. The party’s newly drafted 2016 platform parrots Senator Sanders’ strident Socialist rhetoric, and Mr. Sanders is pressing party brass to move even farther left.

The platform claims the biggest problem facing our nation is extreme inequality. That diagnosis is wrong. What ails America is something else: economic immobility. The Democrats’ platform would make it worse.

Americans who are stuck on the bottom rungs of the ladder are justifiably enraged. Yet they’re not angry at the rich. They’re frustrated about working harder than ever, and not moving up. The system feels rigged. The American dream promises that no matter how humbly you start out, with hard work you can succeed and see your children go even higher.

Sadly, it’s not actually happening in our country. That’s the major takeaway from Francis Buckley’s riveting new book, “The Way Back.” Mr. Buckley shows that wrongheaded policies are limiting economic mobility here, dropping the U.S. below most European countries and Canada. .

The Democrats’ 2016 platform doubles down on these policies: over-taxation, lax immigration standards, and slavish protection of the public school monopoly.

Start with the party’s tax platform — an anti-business rant — like Bernie Sanders channeling Eugene Debs and Karl Marx. “At a time of massive income and wealth inequality,” it states, “we believe the wealthiest Americans and largest corporations must pay their fair share in taxes.”

Fair? America already taxes corporations at higher rates than most countries — one reason the Obama economy limps along at 1.7% annual growth while countries with lower corporate taxes are doing far better. Meager growth here means fewer job opportunities and less mobility. The platform literally never mentions economic growth and ignores the causal connection between high taxes and the current economic malaise.

Democrats threaten they will make “American corporations pay U.S. taxes immediately on foreign profits” so they can “no longer escape paying their fair share … by stashing profits abroad.” That’s a red herring. Most countries don’t even tax profits made outside their borders.

Reckless threats like that are likely to make American companies pull up stakes and move, taking jobs with them.

On education, the platform’s adamant defense of the public school monopoly is immoral. Democrats pledge more resources for “pre-K – 12 schools in every zip code” even though there’s no evidence that more spending improves public schools. Teachers in the U.S. are already among the highest paid in the world.

What is obvious is that trapping poor kids in low-performing schools stops the process of economic mobility cold before it can even start. Children of the political elite have plenty of options. The Obamas and Clintons sent their daughters to the tony Sidwell Friends School in Washington D.C. Yet these Democrats oppose vouchers that would give other parents the ability to choose private or parochial schools.

The Democrats’ platform is a shameless surrender to the teachers’ unions. In exchange for the millions of votes these unions can deliver, the party protects incompetent teachers, and locks children into failing public schools.

On immigration, Democrats defend a policy that exacerbates the very thing they whine about: inequality. Democrats support preferences for relatives of people already here. Stressing family ties inevitably brings in droves of unskilled people, along with grandparents and others unable to work. A recipe for more inequality.

Our nation’s policy should be: Show us how you intend to contribute economically and you’ll be welcomed in without regard to your race, national origin, or family connections. As for welfare benefits, Democrats predictably call for expanding them. But the U.S. already doles out more generous benefits than Britain, Canada, Denmark, Norway, the Netherlands, and most other countries, as Mr. Buckley points out.

The Democrats’ platform promises to help more people reach the middle class. But welfare programs won’t do it, and neither will the party’s other proven-to-fail policies. What the nation needs is economic growth. Somebody please tell Bernie.