Consider Abraham: “He believed God, and it was credited to him as righteousness." Understand, then, that those who believe are children of Abraham. The Scripture foresaw that God would justify the Gentiles by faith, and announced the gospel in advance to Abraham: “All nations will be blessed through you.” So those who have faith are blessed along with Abraham, the man of faith. Galatians 3:6-9 NIV 1984Election, as biblically referenced, hearkens back to Abraham and what was promised to him. Abraham was hand-picked by God to be the father of a people through Sarah, who were to be given a land in perpetuity in Canaan, and who would have God as their god and who would be God's people. Through him/them would all the world be blessed. Abraham's heirs through this promise, therefore, were a people chosen by God to be savingly related to him--the elect.
Within God's covenants with Abraham, however, a potential division of his progeny was intrinsic, for "God would be their god" is an inherently conditional statement. God can only be one's god if he is believed in, trusted, and followed in obedience and fellowship uniquely by those for whom he is their god. If those characteristics are not in place, then neither can it be said that God is their god. A cultural myth, part of background perhaps, but not a personal god.
This division is what Paul exploits in Romans 9. There seems to be an assumption packed by Paul into v 6 which would represent, it seems to me, a "Jewish" way to see election. Jews, the sons of promise, the possessors of Israel, the nation affiliated with the worship of God would be expected to be those who would embrace their promised Messiah, the blessing to all nations. That was not happening and therefore it called into question the word of God regarding their election and the promise to the elect.
If the foundation of election in Abraham would have been understood by those making such an assumption, then the assumed misunderstanding could have been avoided. Paul spent chapter 9 of Romans trying to get this point across. Salvivic election, NT election--the election of Abraham (if I can put it that way) is predicated on faith. God chooses all those who trust his promise, Jew and Gentile alike, to be saved.
Instead, the "Jewish" approach to election seems to be dominated by Mosaic concerns. God picked Israel, corporately, to be delivered from bondage, ensconced in the Promised Land, governed by the law and blessed. Circumcision and nominal adherence to the Law was all that was necessary to secure what was promised, and if Messiah came it would have been obvious to them. The Jews would have followed him as a people into the golden age of Israel.
What is missing in such an understanding is the transitory nature of the Mosaic Covenant. It was nothing more than a schoolmaster, a temporary regimen meant to ensure that an anticipated goal could actually be reached. A "Mosaic" understanding of election can embrace a purpose in time for national Israel, but let us be clear--Moses has nothing to say about Abraham...
Is the law, therefore, opposed to the promises of God? Absolutely not! For if a law had been given that could impart life, then righteousness would certainly have come by the law. But the Scripture declares that the whole world is a prisoner of sin, so that what was promised, being given through faith in Jesus Christ, might be given to those who believe. What, then, was the purpose of the law? It was added because of transgressions until the Seed to whom the promise referred had come. The law was put into effect through angels by a mediator. A mediator, however, does not represent just one party; but God is one. Before this faith came, we were held prisoners by the law, locked up until faith should be revealed. So the law was put in charge to lead us to Christ that we might be justified by faith. Now that faith has come, we are no longer under the supervision of the law. You are all sons of God through faith in Christ Jesus, for all of you who were baptized into Christ have clothed yourselves with Christ. There is neither Jew nor Greek, slave nor free, male nor female, for you are all one in Christ Jesus. If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise. Galatians 3:19-25 NIV 1984So if we see Abraham's promises from God in the broadest sense, Abraham's election was sealed by faith as is that of all those (Jews and Gentiles) who follow in his steps as chosen by God and made righteous by faith. No one is elect unto anything salvivic apart from faith. As for Israel under Moses, they had a role to play (i.e. they were chosen to serve), which is over now, but despite their current rejection of Messiah, God retains plans for them to embrace him en masse finally, one day.