Some theologians consider this call an “effectual or irresistible call.” Their reason is, if God has elected you, that is, picked you out from the human race, when He calls you, you will respond positively to His invitation. Others believe that if you respond to His call, because of His foreknowledge, He elects you. In one sense you don’t need to be caught up in this dispute. If you have responded to God’s call by faith, and received Jesus Christ as your Savior you have been elected. 

To make your calling and election sure involves what commentator Alford says, “for both (the calling and election) in as far as we look on them from the lower side, not able to penetrate into the counsels of God, are insecure unless established by holiness of life. In His foreknowledge and purpose, there is no insecurity, no uncertainty; but in our vision and apprehension of them as they exist in and for us, there is much insecurity and uncertainty, until they are pointed out.”