Apparently most pollsters don't have access to bibles, and probably wouldn't read it if they did have access to one. If they did they would know that the terms "born again" and "evangelical" don't constitute an either-or proposition. Every authentic Christian, evangelical or otherwise, has been born again or else he/she would not be a Christian.
Jesus himself said to Nicodemus "Except a man be born again, he cannot see the kingdom of God", the doctrine that is to me the very essence of biblical Christianity. Good works are worthy of reward after salvation is secured through belief in Jesus' claim that He is God's own divine Son, 2nd personage of the Holy Trinity come to earth in human flesh yet without sin. But good works have no part in the doctrine of salvation by grace through faith alone in Jesus Christ alone as the sinless virgin born Son of God who gave His life on mankind's behalf to pay the death penalty for our sin.
Maybe I'm being too picky about this seemingly trivial matter. However, so much has been said about and written about the term "born again" in disparaging terms by enemies and critics of biblical Christianity and those of us who believe in the veracity of Holy Scripture that I may have become overly sensitive to the implication that all Christians are ignorant hillbillies who are too simple minded and/or uneducated to realize that God is a mythical being who was venerated by many people in the past, but is now known to be nothing more than a pre-Darwin myth by all people everywhere other than a few southern America backwoods folk who topped out at 5th grade or below before dropping out to help Pa feed the hogs and tend the moonshine still.
“Every authentic Christian, evangelical or otherwise, has been born again or else he/she would not be a Christian.”
This is indeed the truth, and i understand your contention, but the problem remains that “Christian” came to denote most anything that calls itself that, and thus such as those who were converted out of mere forms of that word sought to distinguish themselves.
And while I do not think the pollsters have much use for the Bible, yet they did not make these distinctions, but as they existed with manifest distinctions, then it is within their purview to report these and quantify them, although calling anything Christian that is not “born again and evangelical” is misleading.