That's what I thought too. You can't stop preaching even if election is predestined.
God has also ordained the means of Election, namely preaching, See Romans 10:13-15.
The visible evidence of one's election is obedience.
Agreed
1Cr 1:21 For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.