"New evangelicalism" describes a mindset or a philosophy that came into being in the mid to late 40s and early 50s. It originally arose because some of "Evangelicalism" (what today are called "Fundamentalism") thought that evangelicalism was too negative and separatistic, too uninvolved in social issues, and too academically unrespected. So a group of evangelicals set out to become a "new kind of evangelical" or a "new evangelical." The dividing line between the evangelicals/fundamentalists and the new evangelicals was essentially their response to false teachinr (or at the very least differing perspectives). While both the evangelicals and new evangelicals professed virtually identical belief in the essential doctrines of Christianity, the evangelicals were willing to expose and separate from false doctrine; the new evangelicals were not (that is simplistic, I know, but you get the general picture). Over the early years, some of the doctrines of new evangelicals began to suffer (most notably the doctrine of Scripture; cf. Fuller Seminary and Black Saturday, Marsden's Reforming Fundamentalism, Lindsell's Battle for the Bible, etc.).
I am not a new evangelical. I consider myself a historic fundamentalist, in the old style, as much as one can be today. The new evangelicals of yesterday are not considered evangelicals. The evangelicals of yesterday are now called simply fundamentalists (although not all who are called fundamentalists are truly the evangelicals of yesterday).