Former federal prosecutor Andrew C. McCarthy noted at National Review on Thursday that then-President Barack Obama’s administration asked Ukraine to investigate Donald Trump’s campaign manager, Paul Manafort, in 2016.

McCarthy notes the double standard — that Democrats want to impeach Trump for doing what Obama did — and which they have been telling the world for years was necessary to do to protect American national security.

As House Intelligence Committee chair Rep. Adam Schiff (D-CA) told NBC News in March, his investigation into Trump dealt with “a present threat to our national security — whether the president and anybody around him are compromised by a foreign power.” If Trump colluded with Russia, or if the Russians had compromising information about him, they could hold enormous influence over the Trump administration — hence the need for investigation.

That is how Democrats defended the decision by intelligence and law enforcement officials under President Obama to conduct surveillance of Trump campaign associates — without warning Trump himself in a “defensive” briefing.

McCarthy notes that “the Obama administration’s law-enforcement agencies pressured their Ukrainian counterparts to revive a dormant corruption investigation of Paul Manafort” in the middle of the 2016 presidential election.

He cites his recent book, Ball of Collusion: The Plot to Rig an Election and Destroy a Presidency, recently excerpted on Fox News, which reports that Obama administration officials urged Ukrainian prosecutors to investigate Manafort — which amounted to “effectively meddling in the American presidential election.” The results were soon clear: leaks about Manafort’s activities in Ukraine began to appear in the U.S. media, spun in the worst possible light. He was replaced at the Trump campaign and became a target in the phony “collusion” narrative.

McCarthy notes the glaring double standard: “When the Obama administration leans on Ukraine for help in an investigation of political opponents, the Democrats and the media say, “But look how corrupt Paul Manafort was!” When the Trump administration leans on Ukraine for help in an investigation of political opponents, the Democrats and the media say, “Abuse of power — impeach him!”

Two key differences: there is actual evidence of former Vice President Joe Biden extorting the Ukrainian government; and Trump has released the transcript of his conversation with the new Ukrainian president. Only one administration has been transparent.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He earned an A.B. in Social Studies and Environmental Science and Public Policy from Harvard College, and a J.D. from Harvard Law School. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.