I don't know of any other "elect" the prophets spoke of except the Israelites.
Since Jesus basically says to trust what the prophets said, so I believe that elect folks can fall away because the prophets said they could and did.
In fact, I don't know of any NT writer that did not use what the prophets taught to prove their point.
We already know that Paul explained that any branch of the tree could be cut off for changing into an unbeliever and could be grafted back in for changing back into a believer.
We have several NT writers encouraging believers to stand firm in their belief till the end and not go astray.
So I'm gonna tell folks the same thing and use what the prophets taught as proof.
You say all of that in the direct context of the Old Testament Israel, not the Gentile-inclusive REAL Israel. I think you know and agree that there is a difference. The specific reference you mention has Paul, though speaking to the gentile converts, speaking on the OT theme in the context of Jew vs Gentile. The Jews were a proud lot, despising the Gentiles as outside God's graces. The Gentile converts were running the risk of returning the same to the God-abandoned Jews who had rejected Jesus. This is not a statement concerning individuals' obedience, but a statement concerning a group attitude and self-exaltation.
The several NT writers "encouraging believers to stand firm in their belief till the end and not go astray" does not imply that the believers are capable of falling away. It only implies that it is necessary that they see to it that they stand firm and not go astray. As you have probably heard, the fact that something God promises involves human decision and human force of will does not mean it could go differently, but only that God uses (human, in this case), means to accomplish what he is SURE to do.
We see that same principle in the God-hood of Jesus Christ. It was not because he was God, (I say from a human concept of what God is), that Christ did not succumb to temptation, but because he did it right, unlike us. He resisted by the power of His God and Father and His indwelling Spirit, (thus proving, ironically, that he was God). God does things, showing his power, in the most mundane and weak ways.
I don't begrudge people for thinking otherwise, I just think they are wrong on this point but still consider them my brothers and sisters in the Lord and I'm willing to listen to their thoughts on the matter.
That's what a good theology site includes: exchanging thoughts around the warm campfire with others that like to talk about bible stories.
It's what I love to do, and frankly I don't care if anyone disagrees with my perspective; in fact I expect it to happen from time to time.
A big Kum-by-yah moment?
(Just kidding).
I agree, and that is very good. I would urge you to try to look at it from God's perspective, as much as is possible. While I grant the necessarily speculative (and small) nature of US trying to do GOD's perspective, we do know for sure that our human POV is necessarily inaccurate and tiny, compared to God's POV, which is, in the end, the only truth. God will accomplish whatever he has set out to do. We know that what he set out to do with OT Israel was not an attempt to take the genetic nation to live with him in Heaven, and we know that those he has chosen for himself to forever be with him and he with them, he will take to be with him in Heaven.
I know you don't think his arm is too short to accomplish what he wants. What he wanted for OT Israel was exactly what he got --a nation demonstrating their continual inability and unworthiness, and his grace; though he was a husband to them, they were unfaithful. What he wanted for NT Israel --i.e. the body of believers, the Bride of Christ, his Dwelling Place-- is already accomplished, though we don't yet see it as complete. The one thing, physical---the other, spiritual.
