Abraham must have been a very unpopular man in the society and family in which he was raised. He wouldn't likely have been elected to lead the citizenry of Ur Kasdim. He rejected their worldview, smashed their idols, repudiated their (un)ethical system. Who would vote for Abraham? He was a starry-eyed mystic and philosopher, not interested in pandering to the values and interests of his fellow citizens.
A Midrash tells a story that Terah, Abraham's father, was not only an idolater, but did business manufacturing and selling idols. One night, the young Abraham went into his father's shop and smashed all the idols, except one. In that last idol's hand, Abraham placed a hammer. When Terah went to his shop the next morning, he was shocked to see the idols broken to pieces. He asked Abraham: who could have done such a terrible act of vandalism? Abraham answered: the idol holding the hammer must have smashed the other idols. Terah responded: that's impossible, that idol is made of stone, it can't do anything. Abraham retorted: if you don't believe a stone idol can smash other idols, why do you believe it is a powerful god? It's just a piece of powerless stone!
Children like this story because it shows how Abraham outsmarted his father, thereby demonstrating the foolishness of idolatry. Abraham thus made his preliminary case for the truth of ethical monotheism.
As we grow older, though, this story requires a more sophisticated interpretation. After all, we do not think that idolaters really believe that their idols are gods. Rather, the idols are symbols of gods. Terah certainly would never have imagined that one of his idols could act autonomously. He would have thought that his idols were symbols of gods, or that in some way the gods' spirits rested within the idols. So he would not have been impressed with Abraham's question and seeming refutation of idolatry. By analogy, we pledge allegiance to the flag--but the flag is just a piece of cloth, with little intrinsic value. When someone burns the flag, though, we are outraged--not because a piece of cloth was set ablaze, but because that flag is a powerful symbol to us of our nation and our values. Terah would have been outraged to see his idols shattered, in a similar sense to the outrage we feel when our flag is desecrated.
Perhaps that Midrash was alluding to a deeper idea. It was telling us something important about Abraham that would have convinced God to choose Abraham to be father of a new nation.
Abraham was living in Terah's household. He knew his father worshipped idols and promoted idolatry. What young boy wants to rise up against his father's values and his father's business? It would have been so much easier for Abraham to hold his peace, and wait until he was old enough to live on his own before he espoused his monotheistic views. Moreover, even if Abraham chose to argue with his father about the worthlessness of idols, why would he have vandalized his father's shop, an action that was bound to generate a lot of discussion and anger among the townspeople? Furthermore, why would he make a public mockery of idolatry while living in a society full of idolaters? It would have been so much more convenient for Abraham to remain silent, to keep his ideas to himself, to respect the mores of his father, his birthplace, his society.
The Midrash is teaching us that Abraham was a powerful, courageous individual who was not afraid to dissent from the majority when he knew that the majority was wrong. Abraham was willing to risk his own comfort by defying the perverse ideas and values of his father and of the entire idolatrous society. He did not just speak out against idolatry: he had the gumption to smash idols, to bring matters to a head. He was not "diplomatic" in espousing belief in one God and in rejecting idolatry.
Thus, when God saw that Abraham was absolutely not "electable" by his community, God decided that Abraham was His man. God "elected" Abraham--a man of incredible personal strength and vision--to set out on the journey, to leave his society, his birthplace, his father's home. God elected Abraham to establish a new nation, with a new vision, a new idealism, a new ethical system, a new way of relating to God.
The words "lekh lekha" are commonly translated: get thee out. But they can also be translated as: go to yourself. In the latter sense, God was telling Abraham: go to yourself, to your own inner core; don't be misled by your father and his society; don't strive to conform and get along. Stand on your own, be true to yourself. If you "go to yourself" and stay faithful to who you are, you will be the father of a great nation.