Will Republicans call witnesses?

As President Trump’s lawyers open the third day of their defense today, an important question hangs over Washington: Will the Republican-controlled Senate agree to hear testimony from witnesses?

Some key Republicans seem to be moving closer to subpoenaing John Bolton, Mr. Trump’s ousted national security adviser, to testify. Their apparent new position comes after The Times revealed that Mr. Bolton wrote in an unpublished manuscript that the president had told him that he wanted to continue freezing $391 million in aid to Ukraine until officials there investigated Democrats.

Trump’s argument: The president’s lawyers maintain that the aid holdup was separate from the requests for investigations, and that he insisted on the investigations out of a concern for corruption in Ukraine.

What’s next: Mr. Bolton has said he would testify at Mr. Trump’s impeachment trial if he were asked to do so. The Senate will vote on whether to call witnesses after Mr. Trump’s legal team wraps up its defense, very likely this week. Here are the latest updates.