If you did a study of election, you would discover that many of the key biblical statements dealing with the doctrine of election come from the lips of Christ. He constantly emphasized the sovereignty of God in the salvation of sinners. This was a running theme in throughout or Lord's earthly ministry—and the gospel of John is packed with important texts that are essential to a right understanding of the doctrines of divine election and the sovereignty of God in salvation.
The doctrine of election is taught by virtually every New Testament author. Paul had a lot to say about it. So did Peter, Luke, and the apostle John. But I think the Person who had the most to say about divine election, irresistible grace, and predestination was Christ Himself. The theme of God's sovereignty permeates His teaching, and he brought it up in every conceivable context. That is one reason I make no apology for emphasizing these doctrines so often myself...