The outgoing senator's opposition to further evidence means that Democrats will almost certainly lack the votes on Friday to issue subpoenas for testimony from witnesses such as former National Security Adviser John Bolton.
Some of Washington's top Democratic leaders continue to warn that without witness testimony at Trump's impeachment trial, an acquittal by the chamber will be "meaningless."
The Trump defense attorney argued that, even if the president withheld aid from Ukraine to push for political probes, it's not impeachable because it's in the quest for reelection and is, therefore, in the public interest.
A trio of Democratic senators—Joe Manchin of West Virginia, Doug Jones of Alabama and Krysten Sinema of Arizona—are considered toss-ups when it comes to whether they'll vote to convict the president.
Democrats and Republicans will submit—unsurprisingly—diametrically opposing questions to Chief Justice John Roberts, with most senators likely already decided what their final vote on removing the president from office will be.
The move by liberal activist group Need to Impeach will seek to exert pressure on GOP senators, specifically those who are considered wildcards when it comes to supporting trial witnesses, such as former National Security Adviser John Bolton.
Democrats' only hope to hear from the former national security adviser could be through his forthcoming book's manuscript.
Here are a few of the claims made by President Trump's lawyers that failed to paint the entire picture.
Just two GOP senators were exceptions—Mitt Romney and Susan Collins—both of whom signaled before the Bolton revelations they'll side with Democrats to subpoena witnesses and documents.
The trial is far from over. Trump's legal defense team will layout a brief preview of their case Saturday and pick back up on Monday. Later next week, senators will have a question-and-answer period and a fierce debate over whether to subpoena witnesses is expected.
Over the course of their opening arguments the past three days, the Democratic impeachment managers have sought to dispel the notion of any wrongdoing by the Bidens with regard to Ukraine.
The clip of McCain, who often drew the scorn of Trump, was yet another example of the impeachment managers using the words of Republicans and some of Trump's staunchest defenders against him.
If Republicans choose to forgo witnesses, they run the risk of additional damning information coming to light after the trial. But the Democratic managers may have alienated the few moderate Republicans who've yet to decide whether they need more evidence.
House impeachment managers use Republicans' words from the past to dispel the notion that a president cannot be impeached for acts that do not amount to crimes.
The likelihood of such a potential deal seems miniscule, as many Republicans have said they don't believe any witnesses are necessary and Democrats say Hunter Biden is irrelevant to hear from.
President Donald Trump is no stranger to appearing on the big screen—and his impeachment trial playing out in the Senate is no exception.
Democrats have acknowledged what may have been their last chance to force subpoenas for witnesses and documents the White House denied to House impeachment investigators has come and gone.
The move to modify a resolution to outline the rules for President Trump's Senate impeachment trial underscored the power that a small group of Republican lawmakers wield over leadership.
Trump's impeachment trial is expected to begin Tuesday afternoon after a heated debate over GOP rules. It comes after a flurry of preparations by both sides over the weekend.
"You can call me a conservative hack, but do you want witnesses, yes or no? Why aren't you telling us?" Fox News' Laura Ingraham asked Martha McSally.
Over the weekend, House impeachment managers and the president's defense team will draft briefs that will lay out each side's argument.
GOP senators appeared apathetic to the news that a government watchdog determined Trump violated the law by withholding aid from Ukraine and that new evidence further detailed the president's efforts to force the ouster of a former ambassador and pressure Ukraine to investigate the Bidens.
GOP Senate leaders, as well as rank-and-file Republicans, don't agree with the president's legal team about seeking a dismissal of the impeachment articles.
The GAO report that said withholding money from Ukraine violated the law came the same day that the impeachment trial against President Donald Trump will officially begin.
Appointing a diverse group of lawmakers to represent their case to the Senate was Pelosi's final act, the last bit of power she wields to convince the Senate that the president has committed impeachable offenses.
For the more than dozen senators who served during former President Bill Clinton's trial and remain in office today, several of them have made contradicting remarks when it comes to the question of whether or not to allow witness testimony.
One reason is that Gabbard has failed to meet fundraising and polling requirements laid out by the Democratic National Committee for the seventh debate, making it the second one in a row she's failed to qualify for.
A floor vote in the House is expected Wednesday to name who the impeachment managers will be and to send the articles to the Senate for a trial.
The administration and Republican-led states want Obamacare to be struck down as unconstitutional, which would have wide-ranging implications for America's health care system.
"Let me be clear: I do not believe Democrats are in love with terrorists, and I apologize for what I said earlier this week," the top Republican on the House Judiciary Committee wrote in a series of tweets.