WASHINGTON — The Democratic chairman of the House Judiciary Committee laid out sweeping accusations against President Donald Trump on Wednesday as the impeachment inquiry entered a new phase, foreshadowing the possibility of a broad set of charges in coming weeks.

Like previous presidents who have faced impeachment, Trump has obstructed investigations into his conduct, said the committee chairman, Rep. Jerrold Nadler (D., N.Y.). On top of that, Trump is the first president facing impeachment for seeking foreign assistance to support his personal political ends, Nadler said, citing testimony of administration aides and career diplomats and foreign policy officials.

Nadler’s statement, delivered before four law professors offered their opinions on the public evidence and historical standards of impeachment, suggested Democrats are likely to cast a wide net as they seek to approve impeachment charges before year’s end.

“Never before in the history of the republic have we been forced to consider the conduct of a president who appears to have solicited personal political favors from a foreign government. Never before has a president engaged in a course of conduct that included all the acts that most concerned the framers” of the Constitution, Nadler said in his opening statement.

His comments began the first impeachment hearing in the committee that could bring formal charges against the president.

Its ranking Republican didn’t contest the facts or defend Trump’s conduct, but accused Democrats of embarking on a partisan crusade meant to overturn the results of the 2016 election and preempt Trump’s reelection.

“You just don’t like the guy. You didn’t like him since November of 2016,” said Rep. Doug Collins (R., Ga.). “Don’t tell me this is about new evidence.… This is nothing new, folks. This is sad.”

He added, “This is not an impeachment, this is just a simple railroad job.”

Nadler cited Trump’s behavior and that of his close allies — withholding nearly $400 million in military aid to Ukraine while pressuring the country’s new president to investigate Democrat Joe Biden and a discredited conspiracy theory about interference in the 2016 election — followed by his refusal to turn over documents to Congress or allow witnesses to testify. Together, they encompassed obstruction, abuse of power and a betrayal of his office for personal gain, followed by improper attacks on witnesses who did testify, Nadler said.

He also invoked Trump’s attempts to hinder the special counsel investigation into Russian election interference, raising the possibility that the conduct laid out months ago by special counsel Robert Mueller could also become part of impeachment charges — though other Democrats have argued for a more tightly focused case based on Ukraine without relitigating other topics.

Trump has said he did not seek a “quid pro quo” with Ukraine’s president, and continued his attacks on the House process Wednesday.

"The word impeachment is a dirty word,” he told reporters as he wrapped up NATO meetings in England, predicting that the push will backfire on Democrats. “This should never happen to a president again, what’s happened here. It’s an absolute disgrace to our country.”

At the House hearing, three professors called by Democrats argued that Trump had committed the most egregious acts of any president to face impeachment, while the one invited by Republicans said impeaching Trump on the evidence available so far would dangerously lower the standards of removal for generations to come. (It is common for the majority in the House or Senate to choose the bulk of witnesses.)

The professors who supported impeachment said the evidence shows bribery, soliciting of foreign election interference, and obstruction of justice and of a lawful congressional investigation.

Trump’s conduct is “worse than the misconduct of any prior president, including what previous presidents who faced impeachment have done or been accused of doing,” Michael Gerhardt, a law professor at the University of North Carolina who is also a visiting scholar at the University of Pennsylvania Law School, wrote in a statement. In his oral testimony, he said, “If Congress fails to impeach here, then the impeachment process has lost all meaning.”

Pamela Karlan of Stanford Law School said Trump’s conduct “struck at the very heart of what makes this a republic to which we pledge allegiance." She added: "Drawing a foreign government into our elections … undermines democracy itself.”

But Jonathan Turley of George Washington University Law School said Democrats did not have enough facts and were moving too fast for an action as grave as removing a president. While saying that he did not vote for Trump, Turley said, “I’m concerned about lowering impeachment standards to fit a paucity of evidence and an abundance of anger.”

He argued that an impeachment with a “facially incomplete and inadequate record” would make it too easy to wield impeachment against future presidents, and accused both parties of acting on mutual fury.

He asked, “Will a slipshod impeachment make us less mad?”

Republicans also questioned the Democratic witness’ impartiality by pointing to their campaign donations to Democrats and writings critical of Trump. And Trump allies accused Karlan of dragging the president’s 13-year-old son into politics when she said, “The president can name his son Barron, but he can’t make him a baron.”

“It makes you look mean and like you’re attacking someone’s family,” said Rep. Matt Gaetz (R., Fla.).

Karlan later apologized, “It was wrong of me to do that,” she said, adding that she wished Trump would apologize for some of his conduct.

Rep. Madeleine Dean, a Democrat and Judiciary Committee member from Montgomery County, rejected the idea that Democrats have moved too quickly.

“I wonder what more evidence it would take,” Dean said during a break in the hearing. “I also never buy the argument of ‘It’s too soon.’ In my mind there is an urgency, because this invitation to interfere in our elections we know is ongoing and will continue."

Rep. Mary Gay Scanlon (D., Pa.), another panel member from Delaware County, said the hearing, while often diving into deep academic waters, laid out the stakes, and explained why the country’s founders included impeachment as a possibility. “It was exactly this type of situation, it was when you have a president who is abusing his office in a way that undermines our democracy,” she said.

The frequently dry, seminar-like discussion over legal history and the constitutional standards of impeachment laid the groundwork for a new stage, edging Democrats ever closer to formally charging the president. If the House Intelligence Committee served as a fact-finding operation in leading the inquiry over the last several weeks, the Judiciary Committee is now charged with weighing those facts, deciding whether they warrant impeachment and on what grounds.

The acrimony already infusing the process seemed sure to ratchet up given the stakes and the makeup of the committee. With 41 House members, it is nearly double the size of the Intelligence Committee, and is known for a more freewheeling and combative atmosphere. The Judiciary Committee is stocked with a wider range of personalities, including some of the most outspoken members of both parties.

In keeping with that reputation, Republicans sought to delay and sidetrack the hearing with a series of parliamentary maneuvers, including one by Rep. Guy Reschenthaler, a Republican representing southwestern Pennsylvania, in which he publicly named a person said to be the anonymous whistle-blower who got the process rolling.

Each move was overruled by the majority Democrats.

Democrats don’t have any further impeachment hearings scheduled yet, but more are expected in short order as they push for a full House vote by Christmas, and the Senate readies for a trial early next year.