The Democratic case against the president is built around four major issues that the president’s critics say prove that Mr. Trump abused his office:
Giuliani and a shadow diplomacy: Current and former diplomats and national security officials have described to investigators how Rudolph W. Giuliani, the president’s personal lawyer, led a shadow foreign policy in Ukraine that circumvented career foreign service officers and established diplomatic channels in an effort to further Mr. Trump’s political agenda.
Mr. Kent told investigators that Mr. Giuliani’s influence over Mr. Trump when it came to Ukraine was “almost unmissable,” and he said Mr. Giuliani led a “highly irregular” channel of policymaking on Ukraine.
The security aid: Congress approved nearly $400 million in security aid to help Ukraine counter Russian aggression. But witnesses have testified that the aid was abruptly frozen at the direction of the acting chief of staff, Mick Mulvaney, and the Office of Management and Budget. They have said they were alarmed to learn that the aid would not be restarted unless Ukraine agreed to publicly announce the investigations that Mr. Trump wanted.
In gripping closed-door testimony, Mr. Taylor recalled having seen firsthand Ukraine’s need for the security aid when he traveled to the country and witnessed its soldiers facing Russian forces across a damaged bridge. He told lawmakers that he knew at that time that “more Ukrainians would undoubtedly die without the U.S. assistance.”
The July 25 call: At the heart of the Democratic case is the reconstructed transcript released by the White House of the July phone call between Mr. Trump and President Volodymyr Zelensky of Ukraine. In the call, Mr. Trump asked Mr. Zelensky, who was newly elected, to “do us a favor” and investigate the former vice president, as well as a conspiracy theory that asserts that Ukraine, not Russia, interfered in the 2016 election to help Democrats, not Mr. Trump.
The call is used by both sides to bolster their arguments. Democrats say it is direct evidence of Mr. Trump’s culpability in the pressure campaign. Republicans note that there is no direct mention during the call of the security aid and argue it falls far short of providing proof that Mr. Trump was involved in abusing his office. Mr. Trump has insisted repeatedly that the call was “perfect” and exonerates him.
The ouster of Marie L. Yovanovitch: Among the most personal moments during Wednesday’s hearing is likely to be discussion of the ouster of Ms. Yovanovitch from her post as ambassador to Ukraine. Several witnesses have testified about a smear campaign led by Mr. Giuliani to damage Ms. Yovanovitch’s reputation and oust her.