RUTHFULLY YOURS

The presidential impeachment trial, the nation’s third in its history, grew out of a July 25 phone call in which Mr. Trump asked Ukraine’s president to announce certain investigations just as he was holding up U.S. aid to the country. Mr. Trump has defended the call as “perfect” and has said he did nothing wrong regarding Ukraine. The aid was later released after bipartisan outcry from lawmakers.

“The American people, and frankly, people all over the world, know it’s a hoax,” he told supporters at a recent rally in Des Moines, Iowa.

Mr. Trump had hoped for vindication in the Senate trial after a House investigation that he had decried as politically motivated. What he got was something less: Amid strong support for his acquittal from his own party, several Republicans also said Democrats had proved that he acted improperly regarding Ukraine.

Mr. Trump was also denied a unanimous verdict from Republican senators, with Mitt Romney of Utah voting to convict Mr. Trump on abuse of power.

“The president is guilty of an appalling abuse of public trust,” Mr. Romney said on the Senate floor before the vote.

The action by Mr. Romney, the 2012 GOP presidential nominee, made him the first senator in U.S. history to vote to convict a president of his own party. In the impeachment trials of Democratic presidents Andrew Johnson and Bill Clinton, no Democratic senators voted to convict.

The White House, which as late as Wednesday morning had been predicting that all Republican senators would vote to acquit the president, was caught off-guard by Mr. Romney’s announcement, aides said. The White House abruptly closed to the media a planned event at which Mr. Trump had been expected to make remarks.

Nonetheless, the Senate vote to acquit among Republicans marked a clear victory for the president, underscoring his primacy in the GOP and among the party’s voters and the end to a process that had hung over his presidency as he seeks re-election in November. Mr. Trump has sent nearly 700 tweets or retweets about impeachment, an average of more than five per day.

Democrats said the acquittal amounted to a defeat for both their party and the institution of Congress, and they warned that leaving Mr. Trump in office would make him free to abuse power again.

“He has compromised our elections and he will do so again,“ said Rep. Adam Schiff, the California Democrat who led the team of impeachment managers. “You will not change him. You cannot constrain him.”

House Speaker Nancy Pelosi (D., Calif.) opened the inquiry in September over the president’s push for Ukraine to announce investigations into Joe Biden, a potential election opponent this year, and his son, Hunter. Mr. Trump and his allies have argued that it was corrupt for Hunter Biden to serve on the board of a Ukrainian gas company while his father as vice president was spearheading an anticorruption effort in the country. The Bidens have denied any wrongdoing. Hunter Biden has said it was poor judgment to take the board position while his father was involved with Ukraine policy.

The Democratic-led House called 17 witnesses and hundreds of documents to build its case, formally impeaching the president in December. A month later, it handed the articles over to the Senate, which heard arguments from House impeachment managers and Mr. Trump’s defense team over about three weeks but rejected calling additional witnesses or documents, speeding Mr. Trump’s acquittal.

Mr. Trump’s impeachment trial, the first not to include witnesses, was swift compared with its predecessors. Former President Bill Clinton’s trial lasted two weeks longer than Mr. Trump’s after senators voted to allow new depositions.

The tightly choreographed Senate trial was upended late last month by new revelations from former national security adviser John Bolton about the president’s pressure campaign on Ukraine. The former official’s revelations in a yet-unpublished memoir briefly raised the possibility a sufficient number of Republicans would join with Democrats to vote in favor of new witness testimony. But Republicans ultimately voted nearly in unison to oppose hearing from Mr. Bolton and other witnesses, moving the trial along to Wednesday’s expected acquittal.

A top House Democrat said Wednesday the House would “likely” subpoena Mr. Bolton and continue the investigation. Mr. Bolton’s spokeswoman declined to comment on whether he would comply with any subpoena.

The trial’s political impact isn’t clear. Mrs. Pelosi spent much of last year avoiding impeachment, telling her caucus it needed to be a bipartisan process and last spring describing the effort as “not worth it.” Her mind changed after The Wall Street Journal reported in September that Mr. Trump had pressed Ukraine’s president in the July call to investigate the Bidens. When centrists in her caucus backed an impeachment inquiry, she announced it would move forward.

A majority of voters said they believed Mr. Trump abused his power and obstructed Congress, according to a Wall Street Journal/NBC News poll published Sunday. Some 49% of respondents said he should be allowed to finish his term, compared with 46% who said he should be removed.

Impeachment also made little impact on Mr. Trump’s job-approval rating, which stood at 46% in the January poll—in line with his rating throughout his presidency.

Despite his public attacks on the impeachment process, Mr. Trump stayed—at Senate Majority Leader Mitch McConnell’s urging—largely on the sidelines of Republican efforts to rally lawmakers against voting for new witnesses and approached his own legal team with a fairly light touch.

The president’s sole recommendation to his team came after the defense’s first day of arguments, an administration official said. After his lawyers argued for two hours, he called with a request: put Pam Bondi on TV more. He told the team he wanted Ms. Bondi, the former Florida attorney general who joined the White House last fall as an adviser on impeachment, to continue arguing his case on TV in the evenings.

Instead, Mr. Trump focused his attention elsewhere. As the trial unfolded last week, White House officials huddled with GOP House members and their aides in a small room in the vice president’s office in the Capitol that one GOP aide described as “mission control.” The president, the aide said, insisted advisers not call it a “war room,” which he said wrongly suggested Republicans were embattled and that impeachment was an actual crisis.

—Lindsay Wise and Michael C. Bender contributed to this article.