With the media and Washington deep in the grips of Impeachment Fever, the race for the 2020 Democratic nomination is taking yet another left turn.

Joe Biden, the Washington Post reports, is trying to figure out how he can enter the Get-the-Rich sweepstakes, which until now was mainly a bidding war between Elizabeth Warren and Bernie Sanders.

The ex-veep’s advisers, says the Post, are weighing coming out for a tax on “transactions such as the sale of stocks and bonds.”

It’s a terrible idea. Then-Mayor Abe Beame called New York’s stock transfer tax of the late ’70s the “largest single obstacle to the competitive position of the New York financial community” and thus a burden on the entire city economy.

And of course Biden’s tax would also hit not just “the rich,” but every American who has a 401(k), pension or similar retirement plan.

This is apparently Biden’s effort to compete with the Warren-Sanders “wealth tax,” which would hit not income or transactions, but everything the target owns.

Warren rolled out her plan in January to target the “richest 0.1 percent of Americans.” The tax would take 2 percent of all household net worth above $50 million, and 3 percent of assets above $1 billion — every year.

Last week, Sanders saw Warren’s bid and raised it while declaring “billionaires shouldn’t exist.” His graduated wealth tax starts kicking it on assets of $32 million, hitting 180,000 families to Warren’s 75,000.

Happily, the idea clearly fails the Constitution’s ban on direct federal taxation of individuals: The 16th Amendment let the feds tax incomes, but only incomes.

It’s also disastrous policy: Nearly every European nation that’s imposed one has opted to repeal it, because the wealthy move rather than pay — or spend some of their cash finding ways to protect the rest.

Even Bernie’s beloved Sweden gave up on the idea in 2007, and Denmark before that. France repealed its in 2017, and Norway is phasing out its wealth tax.

Of course, Warren and Sanders don’t care much whether it would work (or at all about the Constitution). They’re just appealing to the huge Democratic left, which likewise doesn’t care about facts, but only its dreams of redistribution.

And it seems to be working: Warren, at least, is passing Biden in the polls and may now be the front-runner. And so Biden feels the need to offer his own “anti-billionaire” tax, continuing his move far to the left of even President Barack Obama.

At this rate, the Democratic nominee is going to wind up as “electable” as Karl Marx.