President Trump has now been acquitted, but Democrats hope his impeachment will disgrace him “for life” and tilt the 2020 election. Don’t bet on it. Sen. Lindsey Graham has a better idea.

Graham is proposing post-impeachment investigations by the Senate to “get to the bottom” of the Democrats’ impeachment hoax. That will pin the disgrace where it belongs — on the party that dragged the nation through an unwarranted ordeal.

Many Republican senators and Vice President Mike Pence are brushing aside the idea of investigations, saying they want to “move on.” Not so fast. These investigations are essential to uncover how House Intelligence Committee Chairman Adam Schiff engineered the whistleblower complaint and expose the solid reasons Trump had for asking Ukraine about the Bidens’ dealings there. Graham said it’s “important” to find out “if the whistleblower was working with people on Schiff’s staff [who] wanted to take Trump down.”

What’s known is that on July 26, a day after Trump’s controversial call with the Ukrainian president, Schiff hired a friend of the whistleblower to join his staff. Shortly afterward, Schiff’s staff met with the whistleblower and guided him on how to file a complaint.

Media outlets have identified the whistleblower as Eric Ciaramella. He doesn’t deny it.

Fox News’ Laura Ingraham reports that she obtained a series of State Department e-mails showing Ciaramella met with Ukrainian prosecutors at the White House in January 2016, when he served on the National Security Council as a Ukraine expert. The prosecutors were concerned about Hunter Biden’s lucrative position with the corrupt energy company Burisma, which was a target of investigation.

Ciaramella isn’t an unbiased informant, like whistleblowers should be. The inspector general saw “arguable political bias” in the whistleblower’s complaint.

The Senate also needs to examine why Intelligence Community Inspector General Michael Atkinson deemed the obviously inadequate whistleblower complaint “credible” and sent it to Congress — the trigger required for Schiff to launch an impeachment investigation.

Whistleblower regulations say that “second-hand or unsubstantiated assertions” are not sufficient, but that’s all Ciaramella could provide; he wasn’t on the July 25 call. Atkinson testified to the House Intelligence Committee behind closed doors and probably offered answers. But Schiff refused to release Atkinson’s testimony, even to the senators during the trial — a stunning concealment.

Schiff shut down any questioning about the whistleblower, supposedly for the whistleblower’s protection — but in fact to protect himself. No law shields whistleblowers from congressional inquiry.

Weeks ago, Senate Finance Committee staff interviewed an IRS whistleblower who says he heard second-hand that top Treasury officials meddled in the audit of the president or vice president’s tax returns. That IRS whistleblower also lacked first-hand knowledge of misdeeds. Yet House Ways and Means Chairman Richard Neal, a Democrat, used that whistleblower complaint to make his case for getting Trump’s back taxes.

Concocting phony whistleblower complaints is the Democrats’ new weapon of choice.

That’s why the Senate needs to call the impeachment whistleblower. Otherwise, as Sen. Rand Paul warned Tuesday, “we don’t get to the root of how this started.” Unless the impeachment trickery is exposed, it’ll be tried again.

The new inquiry also needs to dig into the Biden family’s corrupt Ukraine dealings — precisely what Trump sought. Democrats claim allegations of Biden wrongdoing have been “discredited.” Not true.

On Monday’s “Today” show, Biden lamely tried to defend his son. But the issue is not just Hunter Biden’s cash haul; Biden himself, as vice president, dispersed millions in taxpayer dollars in Ukraine, including a $20 million loan to a longtime campaign donor to open a luxury-car dealership there.

Graham vows, “I am going to bring in State Department officials and ask them why didn’t you do something about the obvious conflict of interests Joe Biden had? Joe Biden’s effort to combat corruption in Ukraine became a joke.”

What isn’t a joke is putting the nation through impeachment to cover it all up.

Betsy McCaughey is a former lieutenant governor of New York.