I guess the author is making a case that the Jews were elect in the OT and that election was opened up to the Gentiles upon the death and ressurrection of Christ.

I think the main case the author makes is that whenever 'election' is used in the Bible it refers to Corporate election and to try to imply individual election is signified would be false.

This argument most probably opens the door to free-will faith/salvation.

The mercy of God is necessary not only when a person repents, but even to lead him to repent, Augustine