President Trump’s lawyers will complete their third and final day of oral arguments on Tuesday, wrapping up a defense that has sought to give Republican senators reasonable doubt and present them with alternative explanations for the president’s actions toward Ukraine.

Their assignment grew more difficult on Sunday after the revelation that John R. Bolton, the former White House national security adviser, wrote in an unpublished manuscript that Mr. Trump refused to release military aid for Ukraine until the country provided investigative information on his political rivals. That corroborates a central element of the abuse of power charge against Mr. Trump, which accuses him of using his position to pressure a foreign power to interfere on his behalf in the 2020 election.

Now, the question is whether the disclosure will move enough Republican senators to join Democrats in insisting on calling Mr. Bolton as a witness in the impeachment trial.

The basics.

What we’re expecting to see: A summation of the president’s legal defense, including a strong argument against calling witnesses who would shed more light on Mr. Trump’s actions. His legal team will seek to drive home the argument that the House made a shoddy case, and the Senate need not reach in and bolster it by hearing new evidence.