Suppose the president of the US demands foreign leader X have X's state conduct an investigation into corrupt dealings of a family member of a former member of the previous US administration (and a potential rival presidential candidate) - and conditions the transfer of military aid on the carrying out of this investigation. 

Ignore for a moment the specific details of the current impeachment process and the current composition of the House and the Senate.

Can this be considered a "high crime" or "high misdemeanor" according to prevailing legal scholarship?

I am obviously no US constitutional lawyer, but in many respects this seems to me like a borderline/gray-area request even in terms of legitimacy (seeing how it is not unreasonable to strive for corruption investigations, albeit not by foreign states) - and thus, as a crime, it doesn't seem to rise to being "high".

Note: 

* I described *acts*, not *intent*. Perhaps the president did this simply because s/he wanted dirt on a potential political opponent. Perhaps he was personally curious. Perhaps he actually cared about corruption. Perhaps he cares about corruption, but only in order to present the previous administration in a negative light and not in his own administration. etc.
* The answer may include some relevant details from the current impeachment process, but please don't write an answer focusing on President Trump or his impeachment process.
* (this comes up repeatedly) No, the Nixon v. US decision (506 U.S. 224 (1993)) does not recognize a power of Congress to impeach arbitrarily or for flimsy causes.