That was the watchword of our Protestant forefathers almost five-hundred years ago. Twice as long as the existence of the America government.
It meant that only Christ was the Savior of the world. That Christ alone could and does save sinners. This was just a short-hand and positive way for the classical Protestants to deny that there was any other person or way to heaven: neither our works, someone else's works, philosophy, good intentions, sociology, politics, sports... "So then it is not of him who wills, nor of him who runs, but of God who shows mercy" (Rom. 9:16).
Now 57% of Evangelicals polled (amongst 35,000 adults) deny that proposition. But then they've been denying it for years, decades even.
For instance, reflecting on what I was taught as a teen-ager:
1. Pagans who never hear the Gospel can live by the "light of nature" and enter heaven. 2. Infants who die enter heaven by virtue of their supposed innocence. 3. Jews in the OT had to obey the Ten Commandments as grounds for eternal life
I suppose other readers could come up with more well-established "exceptions". These are exceptions that classical Protestants did not accept. No one enters heaven because they are innocent; and no one can earn their way to heaven through their own creative religious ways ("light of nature") or even through God's own Ten Commandments (Gal. 2:15ff.).
With these exceptions (and the pointed lack of historical and biblical training in many churches) it is no wonder many Evangelicals accept other ways to heaven: they already did. We are just following our leaders: Billy Graham & Joel Osteen.
For that matter, why not join the mainline churches--they've denied the exclusive and singular way to heaven for a few generations. The word "Evangelical" is becoming more and more meaningless--stretched beyond recognition. Eventually, many Evangelical churches will unrecognizable from those mainline churches.
Then maybe many will wake up surprised, ready to hear the true Gospel that should have never been a surprise to begin with.