The Pope will make no official endorsements. Not even in the general election, though it's well known he doesn't like Trump. Seriously why would he? He's smart enough to know it would backfire, even if Mayor Pete is not.
Hey Mayor Pete! Separation of church and state includes "nice" religion too. /sarc
The Pope will make no official endorsements. He can come close though.
In April 2016, Bergoglio granted an audience to Bernie Sanders; in that same year, Bergoglio implied Trump was not a christian.