WASHINGTON -- U.S. President Donald Trump won impeachment acquittal in the U.S. Senate, bringing to a close only the third presidential trial in American history with votes that split the country, tested civic norms and fed the tumultuous 2020 race for the White House.

With Chief Justice John Roberts presiding, senators sworn to do "impartial justice" stood and stated their votes for the roll call -- "guilty" or "not guilty" -- in a swift tally almost exclusively along party lines. Trump, the chief justice then declared, shall "be, and is hereby, acquitted of the charges."

The outcome Wednesday followed months of remarkable impeachment proceedings, from Speaker Nancy Pelosi's House to Mitch McConnell's Senate, reflecting the nation's unrelenting partisan divide three years into the Trump presidency.

What started as Trump's request for Ukraine to "do us a favour" spun into a far-reaching, 28,000-page report compiled by House investigators accusing an American president of engaging in shadow diplomacy that threatened U.S. foreign relations for personal, political gain as he pressured the ally to investigate Democratic rival Joe Biden ahead of the next election.

No president has ever been removed by the Senate.

A politically emboldened Trump had eagerly predicted vindication, deploying the verdict as a political anthem in his reelection bid. The president claims he did nothing wrong, decrying the "witch hunt" as an extension of special counsel Robert Mueller's probe into Russian 2016 campaign interference by those out to get him from the start of his presidency.

Trump's political campaign tweeted videos, statements and a cartoon dance celebration, while the Republican president himself tweeted that he would speak Thursday from the White House about "our Country's VICTORY on the Impeachment Hoax."

However, the Senate Democratic leader Chuck Schumer said there will always be "a giant asterisk next to the president's acquittal" because of the Senate's quick trial and Republicans' unprecedented rejection of witnesses.

A majority of senators expressed unease with Trump's pressure campaign on Ukraine that resulted in the two articles of impeachment. But two-thirds of them would have had to vote "guilty" to reach the Constitution's bar of high crimes and misdemeanours to convict and remove Trump from office. The final tallies in the GOP-held Senate fell far short.

On the first article of impeachment, abuse of power, the vote was 52-48 favouring acquittal. The second, obstruction of Congress, also produced a not guilty verdict, 53-47.

Only one Republican, Mitt Romney of Utah, the party's defeated 2012 presidential nominee, broke with the GOP.

Romney choked up as he said he drew on his faith and "oath before God" to vote guilty on the first charge, abuse of power. He voted to acquit on the second.

All Democrats found the president guilty on the two charges.

Both Bill Clinton in 1999 and Andrew Johnson in 1868 drew cross-party support when they were left in office after impeachment trials. Richard Nixon resigned rather than face sure impeachment, expecting members of his own party to vote to remove him.

Ahead of Wednesday's voting, some of the most closely watched senators took to the Senate floor to tell their constituents, and the nation, what they had decided.

Influential GOP Sen. Lamar Alexander of Tennessee worried a guilty verdict would "pour gasoline on the fire" of the nation's culture wars over Trump and "rip the country apart." He said the House proved its case but it just didn't rise to the level of impeachment.

Other Republicans siding with Trump said it was time to end what McConnell called the "circus" and move on.

Most Democrats, though, echoed the House managers' warnings that Trump, if left unchecked, would continue to abuse the power of his office for personal political gain and try to cheat again ahead of the the 2020 election.

Even key Democrats from states where Trump is popular -- Doug Jones in Alabama and Joe Manchin in West Virginia -- risked backlash and voted to convict.

"Senators are elected to make tough choices," Jones said.

Several senators trying to win the Democratic Party's nomination to face Trump -- Bernie Sanders, Elizabeth Warren and Amy Klobuchar -- dashed back from early primary state New Hampshire to vote.

During the nearly three-week trial, House Democrats prosecuting the case argued that Trump abused power like no other president in history when he pressured Ukraine to investigate Biden and his son, Hunter Biden, ahead of the 2020 election.

They detailed an extraordinary effort by Trump lawyer Rudy Giuliani that set off alarms at the highest levels of government. After Trump's July 25 call with Ukraine, the White House temporarily halted U.S. aid to the struggling ally battling hostile Russia at its border. The money was eventually released in September as Congress intervened.

When the House probed Trump's actions, the president instructed White House aides to defy congressional subpoenas, leading to the obstruction charge.

Questions from the Ukraine matter continue to swirl. House Democrats may yet summon former national security adviser John Bolton to testify about revelations from his forthcoming book that offer a fresh account of Trump's actions. Other eyewitnesses and documents are almost sure to surface.

In closing arguments for the trial, the lead prosecutor, Rep. Adam Schiff, D-Calif., appealed to senators' sense of decency, insisting "right matters" and "truth matters" and Trump "is not who you are."

Schiff told The Associated Press he hoped the votes to convict "will serve as a constraint on the president's wrongdoing."

"But we're going to have to be vigilant," he said.

Pelosi was initially reluctant to launch impeachment proceedings against Trump when she took control of the House after the 2018 election, warning against a partisan vote.

But a whistleblower complaint of his conversation with Ukraine President Volodymyr Zelenskiy set off alarms. The president's call was placed the day after Mueller announced the findings of his Russia probe.

When Trump told Pelosi in September that the call was perfect, she was stunned. Days later, the speaker announced the formal impeachment inquiry.

The result was the quickest, most partisan impeachment in U.S. history, with no Republicans joining the House Democrats to vote for the charges. The Republican Senate kept up the pace with the fastest trial ever, and the first with no witnesses. Seventeen ambassadors, national security officials and others had testified in the House.

Trump's star attorney Alan Dershowitz made the sweeping, if stunning, assertion that even if the president engaged in the quid pro quo as described, it is not impeachable, because politicians often equate their own political interest with the national interest.

McConnell braced for dissent, but with a 53-47 Republican majority he refuted efforts to prolong the trial with more witnesses, arguing the House should have done a better job.

Roberts, as the rare court of impeachment came to a close, wished senators well in "our common commitment to the Constitution," and hoped to meet again "under happier circumstances."

Secretary of State Mike Pompeo, who had been drawn into the Ukraine affair, signed off on the Senate judgment later Wednesday. "Tonight, it was my pleasure to sign President ΓåòrealDonaldTrump's full acquittal," he tweeted.

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Associated Press writers Laurie Kellman, Matthew Daly, Alan Fram, Andrew Taylor, Zeke Miller and Padmananda Rama contributed to this report.