The Justice Department said last week that it was looking into whether other countries “played a role in the counterintelligence investigation directed at the Trump campaign.” Current and former Justice officials said that it was not necessarily illegal or untoward for Mr. Trump to ask world leaders to cooperate.

Background: The F.B.I. began examining the Trump campaign’s ties to Russia after Australian officials reported that Russian intermediaries had offered damaging information about Hillary Clinton.

Related: Access to a transcript of Mr. Trump’s call with the Australian leader was limited. Similarly, the July discussion with Ukraine’s president was placed in a highly restricted computer system. Here’s how it works.

Why it matters: The call with Mr. Morrison again shows Mr. Trump using federal law enforcement to aid his political prospects.

Yesterday: House Democrats subpoenaed Mr. Trump’s personal lawyer, Rudolph Giuliani, in their impeachment inquiry. And Senator Mitch McConnell, the majority leader, said a Senate trial would be unavoidable if the House impeached Mr. Trump.