Editor's Note: (Errol Louis is the host of "Inside City Hall," a nightly political show on NY1, a New York all-news channel. The opinions expressed in this commentary are his own. View more opinion articles on CNN.)
(CNN) The first day of the Senate question and answer period showed that the impeachment trial has turned into a tense foot race.
Senate Democrats and the House impeachment managers, building a case for additional witnesses and documents, are trying to keep their case for removal alive, hoping that outside events could make the push for witnesses more compelling and perhaps inevitable.
The strategy seems to be working. Every day of the proceedings brings new revelations of conversations that suggest President Trump had direct involvement in suspending military aid to Ukraine in order to pressure that country to announce an investigation of Joe Biden, one of Trump's principal political opponents. Trump has maintained he did nothing wrong in regards to Ukraine.
Republicans, determined to defend President Trump at all costs, are trying to end the proceedings as soon as possible and hold off the calling of any witnesses.
"They're putting a tremendous amount of pressure on everybody," Sen. Joe Manchin told CNN's Chris Cuomo during a break in the trial.
That's no surprise. Republicans know that new evidence will put pressure on wavering members -- especially those who are facing tough re-election battles in the fall -- to allow information damaging to Trump's case to become part of the official trial record.
The leaking of excerpts of the forthcoming tell-all book by John Bolton made it harder for Republicans to refuse to call Bolton as a witnesses. It became even tougher for them when Rep. Eliot Engel, the Democratic chairman of the House Foreign Affairs Committee, disclosed that Bolton once asked Engel and his House colleagues to investigate the firing of the US ambassador to the Ukraine.
"President Trump is wrong that John Bolton didn't say anything about the Trump-Ukraine Scandal at the time the President fired him. He said something to me," Engel said in a public statement. "He and I spoke by telephone on September 23. On that call, Ambassador Bolton suggested to me—unprompted—that the committee look into the recall of Ambassador Marie Yovanovitch. He strongly implied that something improper had occurred around her removal as our top diplomat in Kyiv."
The note from Engel cries out for further explanation -- the kind of information best gathered under oath. Republicans can't afford to have a daily string of such revelations. No wonder they are pushing to round up 51 votes for ending the trial with no witnesses.