But it goes much deeper than that. New reporting shows that Mr. Trump and his lawyer Rudy Giuliani ran what amounted to a shadow foreign policy in Ukraine that unfolded against the backdrop of elections in both countries. Here’s a timeline of events since January.

On Friday, House Democrats issued their first subpoena in the inquiry, requesting documents from Secretary of State Mike Pompeo. And Mr. Trump’s special envoy for Ukraine resigned. He is expected to be interviewed in connection to the House’s impeachment inquiry in coming days.

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