We don’t yet know whether President Trump delayed some military aid to Ukraine as leverage to get Ukraine’s president to reopen an investigation into Hunter Biden. But if we are concerned about U.S. officials inappropriately threatening aid to Ukraine, then there are others who have some explaining to do.

It got almost no attention, but in May, CNN reported that Sens. Robert Menendez (D., N.J.), Richard Durbin (D., Ill.), and Patrick Leahy (D., Vt.), wrote a letter to Ukraine’s prosecutor general, Yuriy Lutsenko, expressing concern at the closing of four investigations they said were critical to the Mueller probe. In the letter, they implied that their support for U.S. assistance to Ukraine was at stake. Describing themselves as “strong advocates for a robust and close relationship with Ukraine,” the Democratic senators declared, “We have supported [the] capacity-building process and are disappointed that some in Kyiv appear to have cast aside these [democratic] principles to avoid the ire of President Trump,” before demanding Lutsenko “reverse course and halt any efforts to impede cooperation with this important investigation.”

So, it’s okay for Democratic senators to encourage Ukraine to investigate Trump, but it’s not okay for the president to allegedly encourage Ukraine to investigate Hunter Biden?

And then there is Joe Biden. In 2016, the then-vice president threatened to withhold $1 billion in U.S. loan guarantees to Ukraine if the government did not fire the country’s top prosecutor, Viktor Shokin. According to the New York Times, “Among those who had a stake in the outcome was Hunter Biden … who at the time was on the board of an energy company owned by a Ukrainian oligarch who had been in the sights of the fired prosecutor general.” The Post reports that it is “unclear how seriously Shokin — who was under fire by U.S. and European officials for not taking a more aggressive posture toward corruption overall — was scrutinizing Burisma when he was forced out.” But what is clear is that Biden bragged about getting him fired, declaring last year: “I looked at them and said, ‘I’m leaving in six hours. If the prosecutor is not fired, you’re not getting the money.’ Well, son of a b –. He got fired.”

This weekend, Biden told reporters, “I have never spoken to my son about his overseas business dealings.” That is flatly untrue. Hunter admitted in an interview with the New Yorker that his father expressed concern about the Burisma post at least once: “Dad said, ‘I hope you know what you are doing,’ and I said, ‘I do.'” Moreover, the New Yorker reports that, “In December, 2015, as Joe Biden prepared to return to Ukraine, his aides braced for renewed scrutiny of Hunter’s relationship with Burisma. Amos Hochstein, the Obama Administration’s special envoy for energy policy, raised the matter with Biden.”

So, Biden was fully aware of his son’s involvement with Burisma when he pressured Ukraine to fire the prosecutor in 2016. He should have known that his using U.S. aid as leverage to force the prosecutor’s dismissal would create, at a bare minimum, the appearance of a conflict of interest.