The problem with this legal theory is that an unlawful quid pro quo is limited to those arrangements that are “corrupt”–that is to say, only those that are clearly and unmistakably improper and therefore illegal. But in the eyes of the law, the specific, measurable benefit that an investigation against the Bidens might bring Trump is nebulous. There is a serious question as to whether it could ever constitute a criminally illegal foreign campaign contribution of personal benefit to President Trump. Indeed, the Office of Legal Counsel and the Criminal Division at the Justice Department apparently have already concluded it couldn’t. Just as important, the U.S. Supreme Court and lower federal courts have struggled since at least the early 1990s with application of the federal anticorruption laws to situations like this, where an “in kind” benefit in the form of campaign interference or assistance is alleged to be illegal.

In my view, a fair and better legal argument can be made in this context that only an explicit, as opposed to an implied, quid pro quo would be sufficient to find criminal illegality as the result of President Trump’s words on the call with President Zelensky. What’s the difference? Instead of President Trump saying to his counterpart in Ukraine in words or substance, “Do me a favor …” he would have to have said, “Here’s the deal …” and followed up by explicitly linking an investigation of the Bidens to the provision of U.S. military assistance. None of that, of course, is what was said.