Calvinism, or the Doctrines of Grace otherwise known as TULIP, is the Gospel.   The doctrine of Imputed Righteousness is the Gospel.  But these are simply fuller expressions of the Gospel.  One does not need to understand all the implications of the Gospel in order to believe the Gospel.  All that's needed for saving faith is for one to recognize that one needs cleansing from sin, and that one needs only to turn from striving to resting in Christ alone as a substitute for all of salvation.  Toplady's famous words from the hymn Rock of Ages are relevant today.

Nothing in my hands I bring,
Simply to Thy cross I cling;
Naked, come to Thee for dress,
Helpless, look to Thee for grace:
Foul, I to the fountain fly,
Wash me, Savior, or I die.

    The five points of Calvinism drive home this simple concept.  They further expound on the implications of this concept.  If one is looking to Christ alone for all of salvation, then they will embrace the doctrines of grace as they are expressed in Calvinism when presented with them.  This is because logically and scripturally, the doctrines of election, limited atonement, irresistable grace, total depravity, perseverence of the saints, and imputed righteousness jive with this simple concept.   And if one argues against these doctrines, it evidences that they do not understand these teachings and/or they do not necessarily believe the Gospel and are looking to some other condition for salvation instead of Christ alone.