President Trump has repeatedly slammed the secret impeachment hearings in the Capitol basement as a “kangaroo court.” Speaker Nancy Pelosi got the message. On Monday, she announced the full House will vote to formally launch impeachment proceedings that will be out in the open, instead of in the dark.

Democrats have been trying to suggest they have the goods on Trump. But fact is, none of the witnesses they have called so far have any firsthand knowledge of presidential wrongdoing.

Behind closed doors and with no media allowed, House Democrats have tried to put on the ­appearance of a legal proceeding. At the end of each session, they leak what they claim happened. The media are all too willing to play along, printing the Democratic pols’ claims as if they were fact.

“Powerful testimony from multiple State and national ­security officials,” The Hill reports, adding up to a “scathing picture of Trump and his allies withholding nearly $400 million in security aid from Ukraine.”

Politico called the testimony of Bill Taylor, the acting envoy to Kiev, “explosive” — though Taylor’s prepared statement merely ­regurgitated what other State ­Department bureaucrats had told him. His source was the rumor mill. It’s called hearsay.

The New York Times reports “a rapidly moving investigation securing damning testimony.” That’s hardly the case. But soon the jig will be up. No matter how many “witnesses” Democrats parade into their hearings, it won’t matter if they have no firsthand knowledge. Even the Times concedes that to ­impeach a president, the House needs proof “tying him directly” to wrongdoing.

Before Pelosi’s announcement on Monday, Adam Schiff, the House intelligence-committee chairman who is overseeing the secret hearings, gave up on calling witnesses who have firsthand knowledge of Trump’s ­negotiations with the Ukrainian president.

Schiff caved after a key witness actually challenged the committee’s subpoena as illegitimate and said see you in court. Charles Kupperman, former deputy ­national-security adviser and one of the few people who was on Trump’s Ukraine call, filed a lawsuit, arguing that the House committee can’t compel testimony for an impeachment until the full House votes to authorize subpoenas for that purpose. That, of course, is the vote Pelosi was dodging.

“We are not willing to allow the White House to engage us in a lengthy game of rope-a-dope with the courts,” Schiff said. Translation: Democrats don’t think they would win in the highest court.

They also don’t want to risk dragging the inquiry on for months, as they did with the Mueller investigation. Better to ram anything through. After all, without evidence of grave wrongdoing, the Republican-controlled Senate won’t remove this president from office. But Dems have one goal — to impeach Trump, damaging him sufficiently to tip the 2020 election.

Schiff’s cynical decision not to meet Kupperman in court indicates he also may not want to press for testimony from Secretary of State Mike Pompeo, or Energy Secretary Rick Perry, or former National Security Adviser John Bolton — men who actually know the facts about Trump’s dealings with the Ukraine.

Additional witnesses are scheduled to appear before Schiff’s committee later this week. But they will offer more of the same. “It’s always people who talked to people who have talked to other people who think that he might have meant this,” says Rep. Mark Meadows, an intelligence-committee member witnessing the charade.

The public isn’t stupid, and Pelosi is a far better politician than Schiff. Polls show fewer than half of voters supporting impeachment in key swing states like Wisconsin, Florida, Pennsylvania and Michigan. These are states Trump won in 2016, and Pelosi has been reluctant to put Democratic members from these states on the spot. Trump called her bluff.

Now the Democrats will have to put up or shut up.

Betsy McCaughey is a former lieutenant governor of New York.