But success in a mission of this size may only bring limited and evanescent political benefits.
But that support was evanescent; it's already back below 50%, and probably still falling.
They are imagined as disembodied spirits, and are often visualized as vague or evanescent forms; hence, the white sheet routine.
evanescent ev·a·nes·cent (ěv'ə-něs'ənt)
Of short duration; passing away quickly.