"If the president does something that he thinks will help him get elected, in the public interest, that cannot be the kind of quid pro quo that results in impeachment," Alan Dershowitz, a celebrity Harvard University professor, told senators.
GOP Texas Senator Ted Cruz had asked Mr Dershowitz, whom Mr Trump used to watch on Fox News, if a commander in chief ordering a quid pro quo is legally appropriate. The question also touched on a sitting president acting, at least in part, while thinking the this-for-that deal might help on Election Day.
"Every public official I know believes that his election is in the public interest," Mr Dershowitz replied. "Mostly, you're right."
"If you say you can't hold a president accountable in an election year where they're trying to cheat in that election, then you are giving them carte blanche," Mr Schiff said. "All quid pro quos are not the same. Some are legitimate and some are corrupt."
Mr Dershowitz's argument is part of a broader Trump team claim that the president did nothing wrong in his Ukraine policy efforts – and even if he did, his actions were not impeachable.
Democrats, however, have based their case on the opposite. One of the impeachment articles stated Mr Trump's actions amounted to him abusing the powers of his office. During the trial, Mr Schiff and his Democratic colleagues have argued Mr Trump's power abuse was an attempt to "steal" November's presidential election.
As the first day of senators questioning House Democratic impeachment team and Mr Trump's lawyers unfolded, politicians mostly asked questions of the team representing their own political party, often with highly leading questions. None of the questions from the GOP senators suggested any are thinking of voting to convict and remove Trump; it would take 20 joining with the chamber's 47 Democrats.
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