"... a rare opportunity for a global moral voice to influence a leader ..."

Since when has Trump been influenced by any moral voice, global or otherwise? Trump will do what he always does. While he's there he'll talk about how much he admires the pope, and then go back to being the boorish, impulsive, amoral clod we've come to know and... well, know.

Francis would be wise to be polite and stick to his script, but not invest too much energy in hoping this meeting turns out to be substantive. Not much chance of that.