Article II, Section 4 of the U.S. Constitution provides that impeachment shall be for "Treason, Bribery, or other high Crimes and Misdemeanors." Notably, the Framers of the Constitution ruled out "maladministration" as a reason.
In Schiff’s 300-page report, Democrats failed to cite any specific grounds for impeaching the president.
Notably, though Schiff and others attempted to argue that the president had possibly committed "bribery" by allegedly asking the president of Ukraine to investigate former Vice President Joe Biden in exchange for U.S. aid, there is no discussion of bribery whatsoever in the report ‐ other than references to Trump lawyer Rudy Giuliani’s claims that Biden might be guilty of bribery because his son was on the payroll of Ukrainian gas giant Burisma.
The only references to any "crimes" allegedly committed by the president is a discussion of "witness intimidation."
Schiff and his Democrat majority attempt to argue that President Trump committed that crime by tweeting criticism of several witnesses against him, including calling them "Never Trumpers" and drawing attention to their testimony.
The report also cites Trump’s tweets criticizing former U.S. Ambassador to Ukraine Marie Yovanovitch during her testimony, which clearly did not obstruct her testimony and which she would not have known about had Schiff not read them ‐ partially ‐ to her in the middle of the hearing. (Among Trump’s criticisms was that "the new Ukrainian President spoke unfavorably about her in my second phone call with him," which Yovanovitch could not explain.)