Final answer:
A harangue is a long, scolding, aggressive speech, which is what McAdoo and Mencken were critiquing in Harding's verbal style.
Step-by-step explanation:
A harangue is a tirade; a long, scolding, bombastic speech. When figures such as William Gibbs McAdoo and H. L. Mencken criticized Harding's speeches, they were referring to the overblown and empty rhetorical style that can be associated with a harangue. A harangue is characterized by lengthy and aggressive speaking, similar to the "army of pompous phrases" described by McAdoo and the "rumble and bumble" that Mencken critiqued.