The first step to understand divine election is to understand Romans 5, which describes the relationship between the first Adam and the second Adam. (Please click here, and please review the illustrations in hyperlinks that are part of this particular posting.) Romans 5 lays the groundwork for understanding divine election in Romans 9.
If we understand that Christ died for the sins of the entire world, then divine election does not relate to whom and for whom Christ died. (Christ died for the sins of the entire world according to the plain and normative reading of 1 John 2:2.) That is, divine election is not related to an exclusive subset of people whose sins were judged on the cross, but instead relates to those who are "called" to eternal life.
When we understand divine election in this way, at least three things happen:
No sinner can ever make the claim that his sins (no matter how egregious) can disqualify him from the elective purposes of God, since Christ died for the sins of the elect and non-elect. The issue then becomes whether or not the sinner will accept God's righteousness, which comes through faith on what Christ did on the cross. Thus faith on Christ becomes the central issue, and not the unworthiness or unacceptability of the sinner.
Since Christ died for all sinners, the idea of divine election is no longer a dichotomy of who is or who is not saved. Instead divine election is now all about eternal security. In other words, when we uncouple the idea that Christ died only for the elect, and accept that Romans 5 says otherwise, then divine election takes on the meaning of eternal security. The several mentions in the New Testament about divine election (those "chosen") are NOT about the spiritual "haves" versus the spiritual "have-nots" -- instead divine election is about the eternal security for those who are saved.
For those who do not believe the message of the good news (that Christ died for sinners that they may be saved), their condemnation is not because they were not loved by God. That is, "for God so loved the world that he gave his only begotten son, that whosoever believes on him may not perish, but have everlasting life" (John 3:16). God is not unjust that some are unsaved, because his love prompted him to sacrifice his son for the sins of the world, which God loved. The same John who wrote the gospel of John wrote the first epistle of John, where he reiterates that Christ died for the elect and non-elect (1 Jn 2:2). Therefore the statement by the Apostle Peter makes sense that God desires that none perish, but that all be saved (2 Pet 3:9). In other words, Jesus Christ loves all sinners for whom he died.
So the crux of the argument becomes, why does not God call all men to salvation, since Christ died for all men? Why are some "hardened" like the Pharaoh of Egypt to their own detriment?
The truth is that God reveals himself to all men through natural revelation (evidence of creation), but that men's hearts are darkened or blinded (Rom 1:18-32), but not because of any shortcoming by God. It is therefore not God's fault that sinners reject him. When we share the gospel that Christ died for all men, we are penetrating this darkness and blindness with special revelation (Word of God), through which God "calls" the sinner to himself (John 6:65). Whether or not the sinner responds to the gospel message will rely on this "call." This "call" is to God's righteousness and God's eternal life, which is the exclusive purview of God to give to those whom he has chosen. The reason that God is just is because the issue of divine election does not revolve around whose sin was judged or not judged on the cross (since Christ died for the elect and non-elect), but concerns those to whom God has willed to share his own righteousness and eternal life through his Son. So while the issue of the atonement of the sins of some and not others could become a bone of contention ("How could God sincerely and ingenuously offer salvation to all men, if the sins of some, but not all, were atoned for?"), the issue of sharing ones righteousness and eternal life is not.
Thus for those who are the elect of God, their realization is that their election is never based on how "good" or "bad" they were, but on the kindness and patience of God toward them (Rom 2:4), which put up with their unbelief up until the day that they were saved. For example, the Apostle Paul, who was so hostile to all things Christian at one time of his life, this realization meant to him that the "demonstration of the perfect patience" of God toward him who at the time was "the chiefest of sinners" (1 Tim 1:15-16). So the answer that we give to the unbelieving world is that the current time is a period of the patience and kindness of God, when he calls the elect, and at the same time it is the period when God also endures with much patience the non-elect (Rom 9:22).
In summary, divine election precludes us (a) from looking down our noses on the unsaved because of their sinfulness since Christ died for both their sins as well as our sins; (b) we understand election in the light of eternal security rather than as a doctrine of spiritual "haves" versus spiritual "have-nots"; and finally (c) we know that God "calls" the elect through his patience and kindness, and so for the unsaved we also have to trust that the patience and kindness of God will yet work (as in the case of the Apostle Paul) to "call" them to eternal life through the gospel. We can only plead with them "as ambassadors of Christ" that they be reconciled to God (2 Cor 5:20).