■ President Trump also openly called on China yesterday to investigate former Vice President Joe Biden, an extraordinary request that mirrored the one he made privately to the Ukrainian president, which is at the center of his impeachment inquiry.

Critics argue that these requests — seeking foreign assistance in discrediting a potential opponent in the 2020 election — are an abuse of presidential power. By asking so publicly, Mr. Trump seems determined to push back against those charges.

“I think it’s crazy to withhold security assistance for help with a political campaign.” That was a text message from the top U.S. diplomat in Ukraine to American officials. It was revealed as part of the testimony of the first witness in the inquiry — Kurt Volker, of the State Department.

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