WASHINGTON — House Democrats sought on Thursday to pre-emptively dismantle President Trump’s core defenses in his impeachment trial, invoking the words of the nation’s founders, Mr. Trump’s allies and the president himself to argue that his pressure campaign on Ukraine was an abuse of power that warranted his removal.
On the second day of opening arguments in the third presidential impeachment trial in American history, Democrats turned to the task of arguing that Mr. Trump’s actions were an affront to the Constitution, and they worked to disprove his lawyers’ claims that he was acting in the nation’s interests, not his own, when he sought to enlist Ukraine to investigate his political rivals.
In doing so, they waded deeply into the most politically delicate aspects of their case, taking a calculated risk in talking at length about Mr. Trump’s targets: former Vice President Joseph R. Biden Jr. and his son, Hunter Biden. The oral arguments underscored the political backdrop of the trial, unfolding only 10 months before the election, and how, regardless of the outcome — almost certain to be Mr. Trump’s acquittal — it is likely to reverberate long after the verdict is reached.
“Impeachment is the Constitution’s final answer to a president who mistakes himself for a king,” Representative Jerrold Nadler, the chairman of the House Judiciary Committee, told a restless and sharply divided Senate, adding: “Impeachment is not punishment for a crime. Impeachment exists to address threats to the political system.”
Mr. Nadler’s words were intended to rebut a central tenet of the president’s legal defense, that he cannot be impeached if he is not accused of a specific crime. On the contrary, Mr. Nadler said, his conduct was precisely the kind that impeachment was meant to address.
Mr. Trump, back at the White House after a trip to Davos, Switzerland, for the World Economic Forum, appeared to take note that the trial had started again, issuing an angry tweet about “Shifty Schiff” — his name for Representative Adam B. Schiff of California, the lead impeachment manager — and “many other Democrat disasters.”
In presentations that stretched from early afternoon into the night, the team of seven Democratic impeachment managers attacked the argument that Mr. Trump’s legal defense team has signaled will be a main piece of their case: that when the president withheld military aid from Ukraine and sought to secure a promise to investigate Joseph Biden, a leading political opponent, he was merely making a foreign policy decision to root out corruption in Ukraine.
Mr. Trump has consistently suggested, without any evidence, that Mr. Biden pushed to remove a Ukrainian prosecutor because who was investigating Burisma, a Ukrainian energy company with a long history of corruption that employed Hunter Biden on its board. But in a detailed presentation, Representative Sylvia R. Garcia, Democrat of Texas, spent nearly an hour debunking the claim, and said that, in fact, the opposite was true.
To begin with, she said, the prosecutor, Viktor Shokin, was “widely perceived as corrupt,” and Mr. Biden was acting in accordance with official American policy, as well as the policy of the European Union, the International Monetary Fund and other international organizations in calling for his removal.
Moreover, Mr. Shokin had already let the Burisma investigation “go dormant,” Ms. Garcia said, so his ouster “would only increase the chance that Burisma would be investigated for possible corruption.” She asserted that neither the elder Mr. Biden nor his son had done anything wrong, and that American officials — and Mr. Trump — knew it.
“Every single witness who was asked about the allegations again said that Biden had nothing to do with it and it was false; they testified that he acted properly,” Ms. Garcia said, adding, “There is simply no evidence, nothing, nada in the record to support this baseless allegation.”
“In short,” she added, “President Trump asked for the investigation into Biden based on a made-up theory that no one agreed with. No one.”
It was, in effect, a defense of one of the Democrats’ leading 2020 presidential candidates and a potential challenger to the president. Mr. Schiff later volunteered that neither he nor his colleagues had a position on the Democratic presidential primary.
Mr. Schiff also brought Mr. Trump into the chamber — at least on video — to use the president’s own words against him, with a clip in which the president called both Bidens “corrupt” and called for Ukraine to start a “major investigation” into them.
“The president has confirmed what he wanted in his own words,” Mr. Schiff said. “He has made it clear he didn’t care about corruption, he cared only about himself. Now it is up to us to do something about it, to make sure that a president, that this president, cannot pursue an objective that places himself above our country.”
But in focusing on the Bidens, Democrats took a strategic risk. Some Republicans have already threatened to call the Bidens as witnesses, even suggesting that they would insist on hearing from them as a condition of agreeing to subpoena John R. Bolton, Mr. Trump’s former national security adviser.
Democrats have refused to consider the idea, and Mr. Biden has said he would not take part in any such swap. And on Thursday, Senator Lindsey Graham, Republican of South Carolina, said he would not “give in to that pressure” from some of his colleagues to do so.
But Mr. Trump’s legal team said the Bidens were now fair game in the trial.
“They have opened the door,” said Jay Sekulow. “It’s now relevant.”
Senator Josh Hawley, Republican of Missouri, said the Democrats’ arguments had made testimony from the Bidens vital.
“If we’re going to call witnesses,” he said, “it’s now clear we absolutely must call Hunter Biden, and we probably need to call Joe Biden.”
In laying out their case against Mr. Trump, the Democrats focused tightly on the first of two charges against him: that he abused his power by trying to compel a foreign power to help him win re-election in 2020 and withheld two official acts — the provision of $391 million in military aid and a White House meeting with Ukraine’s president — in an effort to advance his illicit scheme.
“President Trump exploited our ally, Ukraine, for his own political benefit to the detriment of American national security,” said Representative Hakeem Jeffries, Democrat of New York. “Is that conduct impeachable? The answer is categorically yes. The Senate must hold this president accountable for his abuse of power crimes against our Constitution.”
Democrats expect to wrap up their case on Friday with presentations aimed at proving the second charge: that Mr. Trump obstructed Congress by withholding documents and witnesses and otherwise working to conceal his behavior. On Saturday, Mr. Trump’s defense team is expected to lay out its case.
On Thursday, Mr. Nadler drew on quotes from Alexander Hamilton; from George Washington’s farewell address; and from a 1792 letter to Thomas Jefferson from John Adams that warned of “foreign intrigue and influence” in arguing that Mr. Trump warranted impeachment and removal from office — regardless of whether he committed a crime.
“No president has ever used his office to compel a foreign nation to help him cheat in our elections,” Mr. Nadler said, adding, “It puts even President Nixon to shame.”
Mr. Nadler also turned to Trump allies — including Alan M. Dershowitz, the Harvard Law professor who is assisting in the president’s defense, and Mr. Graham — to make his case, using video clips of their comments from the 1999 impeachment trial of President Bill Clinton to undercut Mr. Trump’s defense.
In one clip, a youthful-looking and unusually soft-spoken Mr. Graham, an impeachment manager during the Clinton trial, explained why a “high crime” — one of the criteria the Constitution sets forth for the impeachment and removal of a president — does not necessarily require breaking a law.
“What’s a high crime? How about if an important person hurt somebody of low means?” Mr. Graham said at the time, adding: “It doesn’t have to be a crime. It’s just when you start using your office and you’re acting in a way that hurts people, you’ve committed a high crime.”
Even before Thursday’s session got underway, it was clear that Mr. Schiff, Mr. Nadler and the other managers had not changed the minds of many Republicans. Senate Democrats were privately expressing concern that they may not get the four Republican votes they would need to bring witnesses and documents into the trial.
If they do not, the case could be over by the end of next week. Publicly, though, Democrats were putting on a good face.
“I am more hopeful than ever that four conscientious, brave Republicans will come forward and tell Mitch McConnell you can’t shut this down without witnesses, you can’t shut this down without documents,” said Senator Chuck Schumer of New York, the Democratic leader, referring to his Republican counterpart.
Mr. Schumer said there were “lots of conversations going on,” but denied reports that any deal with Republicans was imminent.
The rules of the trial require senators to “keep silent, on pain of imprisonment,” and after two lengthy days of first voting on motions on Tuesday and hearing oral arguments on Wednesday, Republicans were growing weary.
Some complained that Democrats were simply reciting the same facts time and time again, more for the television viewing audience than for the audience in the chamber. Senator Richard M. Burr, Republican of North Carolina, handed out fidget spinner toys to his colleagues, ostensibly to ease the boredom — and to deliver a not-too-subtle dig at Democrats.
“They spent a lot of time, they’re well prepared — I just don’t think they have much to work with,” said Senator Roy Blunt, Republican of Missouri. “They’ve got about a one-hour presentation that they gave six hours on Tuesday and eight hours yesterday, so they ought to be getting pretty good at it by now.”
But Senator Tim Kaine, Democrat of Virginia, said the Democrats had good reason to be repetitive: Many senators — not to mention the public — did not pay close attention to the House inquiry and needed to be brought up to speed.
One Republican, Senator John Kennedy of Louisiana, told reporters as much on Wednesday. “Senators didn’t know the case,” he said. “They really didn’t. We didn’t stay glued to the television. We haven’t read the transcripts.”