WASHINGTON A team of newly appointed House impeachment managers marched two charges against President Trump across the Capitol on Wednesday, delivering them to the Senate along with a formal notification that they were ready to begin only the third presidential impeachment trial in American history.
The highly choreographed procession, hours after the House voted almost entirely along party lines to send the articles and appoint the managers, was the beginning of what promises to be a historic, if partisan, impeachment trial, a proceeding that has already opened divisions in the normally staid Senate.
The tribunal, the first impeachment trial to play out in a presidential election year, has the potential to shape Mr. Trumps legacy, to stoke the countrys political polarization and to inject new uncertainty into the 2020 elections.
The 228-to-193 vote to adopt the articles and appoint the managers came almost a month after the House impeached Mr. Trump on charges of abuse of power and obstruction of Congress, formally accusing him of seeking foreign election assistance from Ukraine and then trying to conceal his actions from a House inquiry. Only one Democrat, Representative Collin C. Peterson of Minnesota, joined every Republican in voting no.
Now the trial is set to begin. On Thursday the Senate will invite the impeachment managers to formally exhibit the articles. Once they do, the Senate will summon Chief Justice John G. Roberts Jr. to preside and all senators will take an oath to administer impartial justice.
The Senate must promptly issue a summons to the president informing him of the charges and requesting a response. At the White House on Wednesday, an irate Mr. Trump denounced the inquiry anew as a hoax, and encouraged Republican lawmakers to rally to his defense shortly before the vote.
Id rather have you voting than sitting here listening to me introduce you, he told lawmakers during a signing ceremony for an initial trade deal with China, instructing them to leave if they needed to cast votes at the Capitol against moving forward with impeachment. They have a hoax going on over there lets take care of it.
The process could damage the president, exposing conduct that some voters find unacceptable, but Mr. Trump is almost certain to use his likely acquittal in the Republican-controlled Senate as a complete exoneration and turn the considerable apparatus of his campaign to stoking public outrage over the process. Democrats believe the proceeding will put pressure on Republicans particularly those facing tough re-election challenges to condemn Mr. Trump or risk being cast as an apologist for his misdeeds.
We are here today to cross a very important threshold in American history, Speaker Nancy Pelosi said as she spoke on the House floor before the vote. Regardless of the outcome, she added, Mr. Trump would be impeached for life.
Earlier Wednesday, Ms. Pelosi introduced the lawmakers who would serve as prosecutors, or managers, of the case. Both chambers were also grappling on Wednesday with a trove of new documents related to Mr. Trumps pressure campaign that played into Democrats arguments that any trial must include new witnesses and evidence. More material was expected to be disclosed, according to an official working on the impeachment inquiry.
Time has been our friend in all of this because it has yielded incriminating evidence, more truth into the public domain, Ms. Pelosi told reporters, arguing that the revelations had validated her strategy to delay pressing charges for weeks.
In the Senate, the contours of an unpredictable trial were taking shape as crucial Republicans indicated they would soon debate the issue of whether to call witnesses during the proceedings.
Senator Susan Collins, a moderate from Maine, said she had worked with a cluster of like-minded Republicans Senator Lamar Alexander of Tennessee, Senator Lisa Murkowski of Alaska and Senator Mitt Romney of Utah to ensure a vote on the matter after opening arguments from each side, which Senator Mitch McConnell of Kentucky, the majority leader, has already proposed.
Ms. Pelosi announced an ethnically and geographically diverse prosecution team that will be led by Representative Adam B. Schiff of California, the chairman of the Intelligence Committee who led the Ukraine inquiry.
He will be joined by Representatives Jerrold Nadler of New York, the chairman of the Judiciary Committee, Zoe Lofgren of California, Hakeem Jeffries of New York, Val B. Demings of Florida, Jason Crow of Colorado and Sylvia R. Garcia of Texas.
Several of the lawmakers have courtroom experience of some kind, a quality Ms. Pelosi said she had sought. Two, Mr. Crow and Ms. Garcia, are both first-term members.
The managers met for the first time as a group on Wednesday to discuss strategy in the basement chambers of the Intelligence Committee, where the impeachment inquiry unfolded last fall.
In the coming days and weeks, the managers will try to lift their arguments against Mr. Trump above partisan politics. Their task is twofold.
First they will aim to recreate the highlights of the two-month investigation into the Ukraine matter, relying on testimony from more than a dozen senior American diplomats and White House officials who outlined a broad campaign by Mr. Trump to use the levers of his government to exert pressure on Ukraine to publicly announce investigations into former Vice President Joseph R. Biden Jr. and claims that the Democrats colluded with Ukraine in the 2016 election. The president, they said, ultimately withheld $400 million in military aid earmarked for Ukraine and a coveted White House meeting for its new leader as leverage.
This trial is necessary because President Trump gravely abused the power of his office when he strong-armed a foreign government to announce investigations into his domestic political rival, Mr. Nadler said during a brief debate on the House floor before the vote.
But Republican leaders on both sides of the Capitol appeared unmoved. Mr. McConnell called the Houses three-month Ukraine investigation a pale imitation of a real inquiry. Representative Kevin McCarthy, Republican of California and the minority leader, called the whole process a national nightmare.
Both men also accused Democrats of hypocrisy for their decision to delay bringing the charges for nearly a month after arguing that the threat posed by Mr. Trump to the 2020 election was urgent and demanded speed action to remove him.
I have three questions for my friends on the other side of the aisle, the Democrats, Mr. McCarthy said. What happened to impeachment being urgent? What happened to Congress being on the clock? What happened to the House being derelict in our duty if we did not act immediately?
The trial itself is not expected to start until Thursday, when the managers will most likely exhibit the articles inside the Senate chamber.
Republican leaders have said the proceeding will not begin in earnest until Tuesday, after the long holiday weekend. That will give them time to clear other pending legislative items, including a North American trade agreement, and finish preparing for a process that could consume senators for weeks.
Emily Cochrane contributed reporting.