Unlike past impeachment cases, there was no special prosecutor or independent counsel to look into the Ukraine matter. Beginning in late September, the House Intelligence Committee did so itself, calling more than a dozen American diplomats and administration officials to testify, first in private, then in public. Over the course of the fall, they confirmed and expanded on the facts in the whistle-blower’s complaint, uncovering a broad scheme by Mr. Trump and allies inside and outside the government to supplant long-held American policy toward Ukraine in line with the president’s personal political interests.

Thursday’s debate touched on the finer points of criminal law and constitutional standards for impeachment as lawmakers dug into the details of the case, tussling over whether Trump’s “high crimes and misdemeanors” actually met the threshold for his removal. Republicans said the president’s actions needed to be statutory crimes to warrant impeachment, and accused Democrats of putting forth a vague charge of abuse of power because they had a flimsy factual record to back up their case. They did not concede any wrongdoing.

“The entire argument for impeachment in this case is based on a charge that is not a crime, much less a high crime, and that has never been approved by the House of Representatives in a presidential impeachment before, ever in history,” said Representative Steve Chabot, Republican of Ohio and one of the managers of the impeachment case against President Bill Clinton in 1998. “If that is the best you’ve got, you wasted a whole lot of time and taxpayer dollars because so many of you, Mr. Chairman, hate this president.”

Democrats rejected that theory, arguing that Mr. Trump’s actions were clearly high crimes because they were offenses against the Constitution itself, but could also be construed as criminal violations of the law. Representative Eric Swalwell, Democrat of California, posited that Mr. Trump could be charged with criminal bribery and honest services fraud.

In seeking to clear Mr. Trump, Republicans returned again and again to statements by the president and Ukrainian leaders since the inquiry began that there was no pressure applied by Mr. Trump or felt in Kyiv. They pointed out that Ukraine did not announce the investigations Mr. Trump wanted and that the military aid the president had blocked for months was eventually released and a meeting between the presidents occurred.