"'And Bernie Sanders, who doesn't believe in God ... how in the world are we gonna let Bernie [...]?' asked Mark Burns, co-founder and CEO of the Now Network [...]" opening for Donald Trump. "'Listen, Bernie got to get saved, he's got to meet Jesus. I don't know, he's got to have a coming-to-Jesus meeting,' Burns added [...] ahead of a Trump event in Hickory, N.C."
I sometimes joked to my students that we were living an old joke about the University of Chicago as "Jewish professors teaching Catholicism to classrooms of atheists" — except I needed to explain Protestantism as well, and my students were almost all believing Christians, even if they weren't always very sure of what they believed. .
Anyhow, this much for a "Rich's Notes" cheat-sheet oversimplifying a couple millennia of Christian theology but giving context for what the sort-of Reverend Mr. Mark Banks said about a secular Jew like Bernie Sanders, which would also apply to a religious Jew like Joe Lieberman and maybe to most Roman Catholics and lukewarm Protestants.
First off, there is no salvation unless you make it to the Father. No matter how well you live your life, if you're not with God you're going to Hell to burn forever in the Lake of Fire (or more interesting and baroque torments if Dante got it right). After that,
No one comes to the Father but through the Son. But how do you come to and through the Son?
No one comes to the Son but through Holy Church: By Baptism and the other Sacraments of the Church one is washed free from Original Sin and kept in line for salvation.
Alternatively and simultaneously, "By Faith and Faith alone shall you be saved." And how does one have capital "F" Faith (i.e., the true one)? Well, one experiences Christ and accepts Jesus as one's personal savior (capital "s" optional). Now, does one do that by striving on one's own? How can sinful, fallen, degenerate, innately depraved Man come to Faith?
Not on your own: God saves whom He will save and damns the rest — the great majority. So, By Grace and Grace alone will you be saved, except you probably won't be.
However ... "A tree is known by its fruits," and there are signs of Grace, including one's living a godly, productive, prosperous life in a godly community and gets accepted by a Church that is a gathering of the saved and live by its rules — like in the good old days of Plymouth Colony and Massachusetts among the Separatists and Puritans who left their stamp big time on what became the US of A.
Got it? That's some basics out of your old-time, hard-assed Christianity in the tradition of St. Paul in a bad mood, plus St. Augustine and Luther and Calvin and our own colonial-era Jonathan Edwards and the Mather boys Cotton and Increase.
So of course Bernie Sanders doesn't believe in God in any way that counts, and there's a fair chance you don't either. Or at least that's the mainstream, or at least a central major stream, of Christian belief, with more liberal ideas always around but often losing out. The ideas of St. Augustine became "Catholic"; his competitors got anathematized and excommunicated. The Medieval Church loosened up a bit — for political reasons Dante has a Roman emperor in Heaven — but Martin Luther and the Reformation brought back tougher doctrine (including, with Luther, on Jews).
Personally, I have no problem with such doctrines, except when combined with unCalvinist ideas on free will and choice and the idea that it is the duty of Christians to save the heathen: in which case devout Christians can become annoying. And demanding a US that is a Christian nation where only those who've come to Jesus can hold office — well, that violates the prohibition of religious tests in our Constitution and undermines the USA as a secular Republic that guarantees freedom of religion.