He mentions two prominent attempts at definitions that I (as a lifelong Catholic) had been unfamiliar with: the 1974 Lausanne Covenant (drafted by the late English theologian John Stott) and historian David Bebbington’s “quadrilateral” of essential characteristics, namely biblicism, crucicentrism, conversionism, and activism.
Dalrymple does not formulate a new standard himself, but he makes several vital points, which I’ll outline in abbreviated form here.
First, he argues, “there’s nothing inherently oppressive or intolerant or authoritarian in seeking to identify who is an evangelical and who is not. . . . Any group that wishes to maintain some semblance of coherence over time will need, so to speak, to patrol its borders.”
Second, we should be “leery” of defining Evangelicalism over hot-button issues such as abortion and gay marriage. Important though those issues are, they are “interpretations and extensions of [Evangelicals'] fundamental commitments and not fundamental commitments themselves.”
And third, “saying that Person P is not an evangelical is not at all the same as saying that P is not Christian or does not have a saving relationship with God in Christ.”
You can read the whole post on his blog Philosophical Fragments.