With the impeachment inquiry of President Donald Trump barely underway, the list of incidents to investigate is piling up faster than the U.S. House can issue subpoenas.

But one revelation is particularly noteworthy — Trump's Oval Office meeting in 2017 with Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergey Kislyak. It was disconcerting enough at the time to have the president welcome two high-level Russian officials into the Oval.

What has now surfaced is that during that meeting Trump told Lavrov and Kislyak that he was unconcerned about Moscow's interference in the 2016 election because, in his telling, the U.S. had done the same in other countries, according to the Washington Post. This was the same meeting at which Trump revealed classified information that exposed an intelligence source on ISIS.

As with the now "do us a favor, though" call to the Ukrainian president, in which Trump urged him to help get dirt on a political rival, White House officials took the memorandum of the meeting with Lavrov and Kislyak and buried it in a limited-access file typically reserved for matters of national security, according to the Post.

It is too easy to become inured to this president's continual flouting of convention. But what happened here goes much further. Trump assuring leaders of an adversarial nation that he had no issue with their interference in a U.S. election that ushered him into office is a serious offense. At the very least, it is a dereliction of a president's sworn duty to "preserve, protect and defend" the country he leads. Consider that it came after Trump had been fully briefed by U.S. intelligence on the extent of 2016 election interference, which had been directed at the highest levels of Russian government.

Little wonder then, that Russian President Vladimir Putin now feels free to use the 2020 election as a punchline. Asked during an energy panel Wednesday about a repeat of interference, Putin jokingly replied, "I'll tell you a secret: Yes, we'll definitely do it," adding in a stage whisper, "Just don't tell anyone."

Funny, huh?

More and more, Trump appears to believe anything that coincides with his self-interest is fair, and anything that doesn't is to be rejected and denounced. That means giving a pass to the Russians on past interference, pressuring the Ukrainian president for a favor that advances his personal and political gain, and enlisting the State and Justice departments in attempting to discredit the Mueller investigation. The Ukrainian call was just one part of that effort.

Trump apparently made similar requests of the Australian prime minister and of Britain's Boris Johnson. U.S. Attorney General William Barr and Secretary of State Mike Pompeo — who, it should be remembered, is Trump's former head of the CIA — have been flying to Rome and London to make personal requests for assistance in their "investigation" of a settled FBI investigation.

Trump now is calling the legal and constitutionally recognized impeachment process a coup. To amplify that framing, he has launched an ad campaign to that effect, backed by one of the most massive war chests in modern political history.

This president's fierce resistance to any means of accountability grows more alarming by the day. The House should proceed with its inquiry and demand that members of the administration stand for questioning or face obstruction charges. It is time to reassert, without equivocation, that the rule of law applies to all in this country.