Trump is the first rich and powerful person to hint at what they want as an outcome. They have even invented a brand new term for it, plausible deniablity.
Even if one believes Comey the question is whether a stated "hope" is sufficient proof to meet a criminal test of obstruction. In Comey's testimony there was no threat or offer of a quid pro quo so it sounds like an uphill battle to show obstruction of justice and not merely gross impropriety which is not an impeachable offence.
It says crimes and misdemeanors. Congress can impeach for just about anything, including incompetence in office. Thus, it doesn't necessarily matter if it meets the legal definition of obstruction. Nixon had to resign when it was revealed that he had told Haldeman to ask the CIA to tell the FBI to back off investigating the Watergate break in. No one debated whether it met the four corners of obstruction of justice. Except for Nixon, who told David Frost that he had no "corrupt intent" in making the request. Apparently he did it because of "national security."
