See biography by R. I. Woodhouse (1895).
His approach was that if the subject lived in luxury and had clearly spent a lot of money on himself, he obviously had sufficient income to spare for the king. Alternatively, if the subject lived frugally, and showed no sign of being wealthy, he must have substantial savings and could therefore afford to give it to the king. These arguments were the two prongs of the fork and regardless of whether the subject was rich or poor, he did not have a favourable choice.
Elected officers (MPs and councillors) sometimes may have recourse to a variant on Morton's Fork when dealing with uncooperative non-elected officers (civil servants). This variant asserts that a non-elected officer's non-compliance with the directive of their elected officer must be due to one of two equally unacceptable causes: either the civil servant is lazy or incompetent, or the civil servant is acting willfully or maliciously against the instructions given by his/her elected officer.