On the first charge, one Republican, Senator Mitt Romney, broke rank and joined all Democrats in voting to convict Trump of abuse of power. But the vote fell well short of the two-thirds majority needed to remove a president. Romney voted with his party on the obstruction of Congress charge.
Democrats had accused Trump of abusing his power by orchestrating a pressure campaign to get Ukraine to investigate his political rival, former Vice President Joe Biden. They also accused him of obstructing Congress for refusing to participate in the impeachment inquiry. Trump denied any wrongdoing, repeatedly calling the impeachment a "hoax".
Trump repeated that assertion again shortly after the trial, tweeting he will discuss "our country's VICTORY on the Impeachment Hoax!" in a public statement from the White House on Thursday afternoon.
"The sham impeachment attempt concocted by Democrats ended in the FULL vindication and exoneration of President @realDonaldTrump," tweeted White House Press Secretary Stephanie Grisham.
'Shameful and wrong', but not impeachable
Trump's legal defence in the Senate trial had argued that House Democrats did not sufficiently prove that Trump engaged in the pressure campaign.
Even if Trump did what House Democrats accused him of, many Republicans said it was not a serious enough offence to remove him from office or ban him from running again with only nine months to go before the next US presidential election.
Several Republican senators said the House proved its case and they expressed disapproval of the president's conduct.
"The president's behaviour was shameful and wrong. His personal interests do not take precedence over those of this great nation," Republican Senator Lisa Murkowski said in floor remarks.
Republican Senator Lamar Alexander said in a statement, "it was inappropriate for the president to ask a foreign leader to investigate his political opponent and to withhold United States aid to encourage that investigation."
While acquittal was always the likely outcome, the question of whether the Senate would call witnesses came to a dramatic head last week amid new revelations from former White House National Security Adviser John Bolton about Trump's alleged wrongdoing. After four hours of arguments, the Senate voted to block witnesses and new evidence in a 51-49 vote.
Moderate Republicans faced heavy political pressure from Senate Majority Leader Mitch McConnell and the White House not to break ranks during the trial.
McConnell met privately with Murkowski and convinced her not to vote with Democrats to call witnesses in the trial.
McConnell, speaking to reporters after Wednesday's vote, accused Democrats of using the impeachment trial to try to gain an advantage in winning control of the Senate in November, but called the effort "a colossal political mistake." He also said he was "surprised and disappointed" by Romney's vote.
Asked by a reporter whether it was acceptable for a president to ask a foreign country to investigate a political rival, McConnell declined to answer directly.