The astonishing testimony of William B. Taylor, this country’s top diplomat to Ukraine, shows the depths to which the administration of President Donald Trump has sunk in its efforts to put the president’s personal interests above those of this nation.

Taylor’s 15 pages of testimony, given in closed session to the U.S. House impeachment inquiry committee, lays out in meticulous detail how Taylor came to the queasy but inescapable conclusion that his official mission was at odds with a second, unofficial — and arguably more powerful — group led by Trump’s personal attorney, Rudy Giuliani, who holds no position within the federal government.

It sounds an alarm that should be heeded by every American, for it directly ties Trump to a quid pro quo that put his own re-election interests above national security concerns.

Taylor, who served as President George W. Bush’s ambassador to Ukraine, is intimately familiar with its strategic importance. U.S. foreign policy goals have been well served by aiding Ukrainian security as that nation fights a yearslong battle against Russian aggression.

Taylor, it should be noted, has unassailable credentials that should render him immune to the standard Republican character attacks against anyone who opposes Trump. He has a lifetime of service to his country, starting as a top-of-his-class West Point cadet who commanded a company in the 101st Airbone Division in Vietnam, won a Bronze Star, worked in NATO and the State Department, and served under Republican and Democratic administrations in hot spots around the world.

When he was asked by Secretary of State Mike Pompeo to return to Ukraine as its chief of mission, the lead official for a diplomatic mission abroad, he did not yet know that Giuliani’s forces would undercut him at every turn in their effort to enlist a foreign government in Trump’s re-election push.

Since its forced annexation of Crimea in 2014, Russia has continued to attempt its encroachment of Ukraine, which has depended heavily on U.S. aid in its efforts to fend off Russian aggression and maintain its independence. Imagine Taylor’s horror when he learned that newly elected President Volodymyr Zelensky, seeking an alliance with Trump, instead was subjected to a different kind of aggression — pressure to “investigate” Trump’s top political rival, former Vice President Joe Biden.

Taylor’s testimony goes further, revealing that he was told that Zelensky would have to publicly commit to such action because Trump wanted to put him “in a public box.” Hanging in the balance was $391 million of desperately needed security assistance, with congressional authorization that expired at the end of September. As Ukrainians fought and died to preserve their country, Taylor said he was told the country would have to “pay up” before Trump would “sign the check.”

This kind of behavior is unacceptable, and Trump’s obsession with re-election over this nation’s strategic interests is dangerous. It’s time for Republican lawmakers to search their conscience. Taylor is no stooge or unwitting pawn. He’s a tough, principled public servant who was rightly appalled at what he saw and now is laying it out clearly for others. That takes considerable courage in the face of an administration that demands personal fealty to its leader and wreaks vengeance on those who refuse.

On Wednesday, the president’s lawyers argued in court that Trump is above the law while in office no matter what he does, even if he should, in words the president once used, shoot someone on Fifth Avenue. That same day, a band of House Republicans forced their way into the closed impeachment inquiry committee, in a stunt that violated House rules and delayed testimony for five hours.

With such goings-on, it is more important than ever for Americans to be reminded that among us exist individuals of principle who serve this nation’s best interests, believe in its values, guard its reputation and call out wrongdoing when it jeopardizes the country they love. William Taylor is one of those leaders, and his warning call deserves to be heeded.

This time, don’t rely on brief video clips or even newspaper accounts. Read the testimony for yourself (