“Has God rejected his people? By no means! I myself am an Israelite…” (Rom. 11:1). The fundamental question driving Rom 9–11 is the faithfulness of God as expressed in Israel remaining within the covenant promise.
According to Wright, Paul’s theology here affirms that Paul is not thinking in terms of a ‘replacement’ theology (Gentiles replacing Israel) but of a ‘remnant’ theology. Paul, since he knows himself to be a believer and in the covenant promise, knows that God has not been unfaithful, has not replaced, but has a remnant by grace.

On the question of whether or not “Israel” is “northern 10 tribes” … an issue arises. Paul says he is an Israelite, and from the tribe of Benjamin … and they are part of the southern tribes –though one might argue that all that remained was Judah. But, 1 Ki 12:21 would indicate that Benjamin is part of Judah. Does Paul not correlate being a Benjamite with being an Israelite?
Paul argues from his own experience that Israelites believe — those whom God foreknew are redeemed (11:2).
Elijah is the second argument: the 7000 who did not bow to Baal are redeemed.
Implication: there is a remnant (of Israel?) to this day. Is it believers from the northern tribes (where do you stand on Benjamin?) or is it ethnic Jews who believe or is it those who are in the Messiah? Wright believes the “remnant” is the Church.
Implication two: the remnant is chosen by grace — not of works.