“God shows no partiality”, contended Paul of Tarsus in his epistle to the Romans (2:11). Paul explained that the righteous and holy judgment of God falls on those who do not see fit to acknowledge Him1. God will render to all, first to Jews and then Gentiles, according to what they deserve (2:6).
Gruesomely, the whole world is held accountable because all, both Jews and Gentiles, are under sin. “None is righteous, no, not one,” Paul quoted Psalms 14:1-32, “no one understands; no one seeks for God. All have turned aside; together they have become worthless” (Rom. 3:10-12 ESV). N. T. Wright sum it well, “[t]he whole world is accountable to God: all people are obviously guilty, and must now face God as their judge.”(Wright 2004: 49)
Although according to the works of the law, “all have sinned and fall short of the glory of God”(3:23 ESV), God’s righteousness is revealed to those whom God, in Jesus Christ, chose before the foundation of the world to be holy and blameless before Him.
Those, who God foreknew and also predestined to be conformed to the image of His Son, are said to have been called, justified and glorified, according to the riches of His free gift of grace, through redemptive work of Christ Jesus (Rom. 8 cf. Ephes. 1:3-11). Craig S. Keener, I suppose, errs in using present tense viz., “God choosing people (8:29–30)”(Keener 2009: Amazon Kindle loc.3974). The usage of past tense viz., foreknew, predestined, called, justified and glorified indicates that Paul understood that God had already sovereignly chose His people.
God shows no partiality. His righteous justice is poured to all who have sinned. To those who God elected, their justice, was mercifully poured upon Christ Jesus, nailed at the cross. It was there the holy and righteous wrath of God upon His past, present and future chosen people was poured in full strength. It was there the wrath of God was not only quenched but their debt forever paid by the atoning work of Christ Jesus. It was there the righteous wrath of God and His pure everlasting love for His people shined the most.
At the cross, Christ Jesus reconciled those whom God the Father gave Him (John 6:44 cf John 17) from the wrath to come. (1 Thes. 1:10) Through Christ atoning work, He, in love, saved them from the wrath of God. (Ro. 5:10)
Romans 9:14’s disturbing question of God’s fairness emerged from the idea that it was from eternally past, before the foundation of the world, that God according to the good pleasure of His will and in love, not only elected His people but also predestined them for adoption as sons in Christ Jesus to be holy and blameless before Him. (Eph. 1:3-7) His choice, accord to Paul, was not based on foreseen character of the elects, but God’s alone.
Readings of Roman 9:1-13 that does not trigger a reader to question God’s righteousness in electing His people can be said to have failed to grasp Paul’s case. The notion that given prevenient grace God chose those who He foresaw would freely choose Him, for example, appears to be incorrect because not only would it make Paul’s answers, namely God has mercy and compassion on whomever He has mercy and compassion (9: 15-16a) and that God’s choice did not depend on the subject’s foreseen response, one who runs, but solely on God (9: 16b-16c), offbeat but also his anticipated question of prima facie unfairness of God (9:14) uncalled-for.
The plausible understanding of Romans 9:1-13 that calls for Paul’s anticipated question and answers, I think, is that which view God’s sovereign election based on the character of God and not of the elects. It is God “who saved us and called us to a holy calling, not because of our works but because of his own purpose and grace, which he gave us in Christ Jesus before the ages began”(1 Timothy 1:19 ESV)
Is God impartial? No. The demanded justice for the wages of sin is given to all without partiality. The wages of those who He chose in His Son were fully paid by the life, death and resurrection of Christ Jesus. God’s mercy lavished upon those whom He chose is simply an amazing grace that cannot be demanded to be given to all.
Keener, Craig S. (2009) Romans. A New Covenant Commentary. Cascade Books – Eugene, Oregon. Amazon Kindle Edition.
Wright, N. T. (2004). Paul for Everyone: Romans Part 1: Chapters 1-8. Both volumes include glossaries. London: Society for Promoting Christian Knowledge.
 Those whom He has gave them up to a debased mind to do what ought not to be done, and they are they who are filled with all manner of unrighteousness, evil, covetousness, malice, envy, murder, strife, deceit, gossips, slanderers, haters of God, insolent, haughty, boastful, inventors of evil, disobedient to parents, foolish, faithless, heartless and ruthless (Romans 1).
 Repeated in 53:1-3