Some suspect Mr. Trump is once again catering to Mr. Putin, who is dedicated to undermining Ukrainian democracy and independence. But we’re reliably told that the president has a second and more venal agenda: He is attempting to force Mr. Zelensky to intervene in the 2020 U.S. presidential election by launching an investigation of the leading Democratic candidate, Joe Biden. Mr. Trump is not just soliciting Ukraine’s help with his presidential campaign; he is using U.S. military aid the country desperately needs in an attempt to extort it.

The strong-arming of Mr. Zelensky was openly reported to the New York Times last month by Mr. Trump’s personal lawyer, Rudolph W. Giuliani, who said he had met in Madrid with a close associate of the Ukrainian leader and urged that the new government restart an investigation of Mr. Biden and his son. Hunter Biden served on the board of a Ukrainian gas company, while Joe Biden, as vice president, urged the dismissal of Ukraine’s top prosecutor, who investigated the firm.