But Mr. Collins’s larger point was that the Ukraine affair had no catchphrase associated with it — and that was somehow telling, both because of the facts underpinning the case against Mr. Trump and because of how it would be remembered.

“What would be known about this one is probably: ‘Where is the impeachable offense?’ ‘Why are we here?’” Mr. Collins said, quoting two lines that have been said by nobody but that broadly speak to the Republican view of the entire process as illegitimate…

Mr. Engel said the lasting catchphrase of Mr. Trump’s impeachment would be “Do us a favor, though,” a line uttered by Mr. Trump during his July 25 phone call with the Ukrainian president, Volodymyr Zelensky, when he asked him to conduct a corruption investigation into former Vice President Joseph R. Biden Jr. The request, in Mr. Trump’s own words, was revealed when the White House released a reconstruction of the call.