Gordon Sondland was supposed to be the key witness in the impeachment drive — the guy who’d nail the coffin shut on Donald Trump’s presidency. Yet his most “damaging” testimony in long hours of questioning Wednesday turned out to rest on nothing but mere assumptions.

Sondland opened the hearing by asserting that Team Trump imposed a “quid pro quo” on Ukraine. He said requests by Trump’s lawyer, Rudy Giuliani, conditioned a White House visit for President Volodymyr Zelensky on a Ukrainian public statement “announcing investigations of the 2016 election/DNC server and Burisma.” And Sondland assumed Rudy was following Trump’s orders.

Eventually, he also “came to believe” that US security aid depended on Ukraine publicly “committing to the investigations of the 2016 election and Burisma,” as Giuliani insisted.

Yet Sondland noted that “we did not think we were engaging in improper behavior” — that no one expressed any concerns. And he admitted that Trump never told him of any “preconditions” for aid or a meeting.

Asked outright, “No one on this planet told you that President Trump was tying aid to investigations. Yes or no?”, he answered, “Yes.”

The followup: “So you really have no testimony today that ties President Trump to a scheme to withhold aid from Ukraine in exchange for these investigations.”

Sondland’s answer: “Other than my own presumption.”

Indeed, when he directly asked Trump what he sought from Ukraine, the president responded: “I want nothing. I want no quid pro quo. Tell Zelensky to do the right thing.”

For weeks, Sondland testified, he saw no link between investigations and aid or a Trump-Zelensky meeting. And, he stressed repeatedly, he had no clue at all, ’til “late in the game,” that Joe or Hunter Biden was remotely tied to any of this.

He also admits his current take on it all is shaped by what he’s read about others’ testimony — not his own recollections.

Sondland was an amiable, charming witness, plainly eager to please each questioner. That may make for a good diplomat, but it rendered his testimony confusing and contradictory — and basically worthless.