Prior to the handshake, Trump walked toward the Saint Ambrose room, led by Gentlemen of his Holiness, which is a sort of honor guard of nobility. Trump arrived Wednesday morning at the Apostolic Palace for an audience with the pontiff. The two men's often opposite worldviews collided head-on early last year, when Francis was sharply critical of Trump's campaign pledge to build an impenetrable wall on the Mexican border and his declaration that the United States should turn away Muslim immigrants and refugees. Papal audiences usually last for about 20-30 minutes of private talks, followed by introductions of delegations, a photo and exchange of gifts. [...] it could provide powerful imagery to Catholic voters back in the United States as well as the possibility for conflict between a president and a pope who have not often seen eye-to-eye.