Explosive and wide-ranging testimony on Wednesday from Ambassador Gordon Sondland makes one thing clear: It is more important than ever that the White House drop its attempts to obstruct justice and intimidate witnesses and instead allow key figures to testify.

Sondland’s testimony implicated Vice President Mike Pence, Secretary of State Mike Pompeo, former National Security Adviser John Bolton, Chief of Staff Mick Mulvaney, Energy Secretary Rick Perry and ringleader Rudy Giuliani, President Donald Trump’s personal attorney. Sondland named all of them as having direct knowledge of the aid-for-investigation scandal involving Ukraine and the White House.

Republican objections to “hearsay” presented by previous witnesses collapsed Wednesday amid Sondland’s insistence under oath that “everyone was in the loop” and that while no one wanted to deal with Giuliani or delay aid to Ukraine, that was the hand dealt them.

Trump and his supporters are relying heavily on Sondland’s testimony that in a brief phone conversation with the president on Sept. 9, Trump said, “I want nothing. I want no quid pro quo” from Ukraine. Context here is important: Sept. 9 was the day the House Intelligence Committee received the infamous whistleblower complaint, with its quid-pro-quo accusation. Trump’s same-day attempt at providing a level of deniability is tissue-thin and hardly the “final word,” as he and supporters insisted on Wednesday.

Trump also said Wednesday that he didn’t know Sondland “very well,” even though he picked him to serve as ambassador to the European Union after he donated $1 million to the president’s inaugural committee.

If the administration hasn’t figured it out yet, revelations in the impeachment inquiry have already hit a tipping point. No amount of stonewalling on its part will make this go away. Republicans can try to discredit Sondland. And former Ukraine Ambassador Marie Yovanovitch. And her replacement, Ukraine Chief of Mission William Taylor. And Lt. Col. Alexander Vindman, U.S. National Security Council director for European Affairs. And their own witness, Tim Morrison, formerly a National Security Council top adviser to Trump on Europe and Russia.

No matter. The public has already seen for themselves that in their testimony those officials largely corroborated one another and the whistleblower complaint. Americans should not settle for less than the whole truth on this disgraceful episode.

To that end, it’s worth noting that Sondland, who is still an official ambassador representing the United States, was blocked by the White House and the State Department from gaining access to notes, e-mails, records and documents that might have helped him prepare for Wednesday’s hearing. Typically, preparation to testify before Congress in such a grave matter is an exhaustive process involving intensive review of any document that could help identify key facts, dates and individuals. Withholding such material is itself an obstruction of justice.

Those implicated by Sondland and others must be made to testify. Ignoring subpoenas should not be an option. The average American ignoring a subpoena would soon face jail and other penalties. Should Giuliani, who arrogantly said, “Let them hold me in contempt,” be held to a different standard?

Among all the spin and counter-spin, the issue here continues to be whether the president withheld congressionally authorized aid to force Ukraine, fighting for its life against Russian aggression, to launch an investigation into his political rival. Sondland testified that there was, in fact, a quid pro quo, and that most top leaders were in on it, understanding that it reflected “President Donald Trump’s desires and requirements.”

No one should be allowed to block, or even hinder, the effort to verify that information and learn if there’s more to the story.