We all know the politics of building a great and beautiful wall on our southern border, yeah?

Democrats say nyet. “There is not going to be any wall money,” according to House Speaker Nancy Pelosi.

President Donald Trump says no wall, no deal to keep government open. “If they’re not going to give money for the wall,” he says, “it’s not going to work.”

So, money seems key here. More so than, say, moral or practical concerns.

If that’s the case, there are alternatives to the stalemate that don’t include declaring a national emergency, or -- as if! -- Mexico paying for the wall.

For example, how about Trump, his fans and multibillionaire pals pay for it?

You want it? You get what you pay for.

A GoFundMe started in December already has $20 million-plus. That’s a start.

Trump’s net worth, says Forbes, is $3.1 billion. Surely, he’d kick in for something. Maybe even a lot if he can put his name on it.

Then he can pinch his uber-rich buddies. There are many. Here are a few.

Vegas casino mogul Sheldon Adelson and wife, Miriam, (net worth $34.6 billion) spooned out $20 million for Trump’s campaign and $5 million for Trump’s inauguration. Bet they’re good for a billion or so.

Wall Street whiz, Trump ally, and former adviser Carl Icahn, whose wife, Gail, was on Trump’s inaugural committee, is worth $17.3 billion. Seems he could help.

And New York Jets owner Robert Wood “Woody” Johnson ($6.3 billion), heir to the Johnson & Johnson fortune, gave $1 million to the Trump inaugural, and was appointed U.S. ambassador to the UK. Maybe a thank you gift is in order.

Then Trump can put these pals together with the five billionaires (combined net worth $33.9 billion) he dined with at his New Jersey golf club last August.

I’m thinking energy tycoon Harold Hamm, real estate giant Richard LeFrak, FedEx founder Fred Smith, New York buddy John Catsimatidis, and Boston Beer king Jim Koch (no relation to the Brothers Koch) can help get to the $5.7 billion wall price pronto.

Now the idea of a privately funded wall can get dicey due to land issues related to eminent domain and property rights.

But David Bier, immigration and border security expert at D.C. think-tank Cato Institute, tells me, “I think it could happen … theoretically, private individuals could buy the property.” He also thinks they could pay for the wall “in cooperation with the federal government.”

Possible snag? The Department of Homeland Security, which has jurisdiction over border issues, can’t accept gifts without congressional approval.

Ah, but if the no-wall argument is we shouldn’t waste tax dollars, wouldn’t it be politically tough for many Democrats to withhold approval and oppose a privately funded wall?

Plus, anybody can gift the government. Since 1843, the Treasury maintains a “Gifts to the United States” account “for individuals wishing to express their patriotism” (or, one could say, wishing to “Make America Great Again”).

And while such gifts are for no-strings, general use, how hard would it be to change that? When it’s about the money, as it always is, Congress does what it wants.

And, even if not, it appears there are other ways to fund the wall.

Back in December, a USA Today op-ed piece by Brett Decker, a former Wall Street Journal editor, and James Renne, a national-security lawyer who worked on Trump’s transition team, noted the U.S. Department of Agriculture holds $200 billion in outstanding loans for rural development projects.

The piece argues these loans to local communities have low default rates and provide a steady stream of revenue. Private investors could, with a lump-sum payment to the government, buy rights to collect the debt. That payment could total tens of billions.

Also, the Washington Examiner last week reported on two existing statutes that might allow Trump to build the wall without congressional approval or a national emergency declaration.

One permits the Pentagon to OK a military construction project if the Secretary of Defense deems it “vital to the national security or to the protection of health, safety, or the quality of the environment.”

The other allows the military to “block drug smuggling corridors across international boundaries,” including through construction of “roads and fences” (maybe big, steel fences?).

The newspaper reports these provisions likely have spending caps around $1 billion. But if used solely for legal authority, surely GoFundMe, Trump and pals can provide remaining construction costs.

No doubt any outside-the-box effort to build the big, beautiful wall leads to litigation. But those who want it most (not most Americans, according to multiple polls), those who believe its value is worth its price? Let them pay for it.