Note that I do not call Donald Trump a Fascist. As far as I can make out, Trump is a political opportunist with no coherent political philosophy.
Nor would I argue that Trump supporters are Fascist, certainly not in a self-conscious way. The question instead is whether the impulse that underpins their support reflects a Fascist sensibility.
This is a question that has cropped up at least since December 2015, as I discovered when I did two Google searches: "Trump fascist" and "Trump not fascist." The early replies were in the negative. See, for example, Dylan Matthews' column in Vox.Com (December 10, 2015): "I asked 5 fascism experts whether Donald Trump is a fascist. Here's what they said." The five experts thought he wasn't.
In January 2016, Gianni Riotta declared in The Atlantic: "I Know Fascists; Donald Trump Is No Fascist." On March 11, The Chicago Tribune also rejected the thesis that Trump was a Fascist. A week later Austin Rise, an historian of Fascism, complained on Breitbart.com that "Claiming Donald Trump Is a Fascist Makes Fascism Impossible to Understand." (March 14, 2016) As recently as May 19, Michael Ledeen sneered in Forbes that "Nobody Knows Anything About Fascism."
By that time, however, Robert Kagan had published a counter-assertion in the Washington Post that gained wide attention, partly because Kagan is a well known defense analyst who is himself conservative (some would say neoconservative) and who enjoys wide respect within the conservative national security community. Pointing to the Trump campaign and the well-springs of its support, Kagan prophesied, "This is How Fascism Comes to America." He argued that however Trump himself characterized his political views, they were essentially fascist and if Trump became President fascism would be lodged in the corridors of national power.
Since then, the op/eds I've encountered has largely followed Kagan's lead. Prominent among them is a long article in the New York Times that places Trump within the larger context of a perceived turn toward global fascism. This morning brings an article in Salon: "Our Memorial Day collision course with fascism: Donald Trump and the new American militarism." "It's not that Trump himself is a fascist," writes David Niose, "but he's a sign that we are more vulnerable to it than we ever imagined."
I offer the above simply as a guide for readers interested in pursuing this story line. I myself am seldom quick to make pronouncements about these things. I do believe that Trump represents a political phenomenon in American life that merits close study--and will undoubtedly receive sustained historical scrutiny regardless of whether The Donald has the opportunity to create the Trump White House. Right now I don't think anyone has a clear handle on what exactly is going on. A number of explanations are floating about, many of which have enough plausibility to serve as legitimate hypotheses. And almost certainly no single explanation will suffice.
Whatever we are looking at, surely it's a perfect political storm, a collision of numerous factors, among them the freakish multiplicity of GOP candidates--if memory serves there were originally 17; Trump's mastery of the cult of celebrity and his ability to captivate the talk radio and television industry; the sheer rage of a segment of the American electorate that feels alienated, betrayed and marginalized for reasons the are class-based; and quite possibly fueled by racial anxieties, nativism, and xenophobia as well . But does any of this add up to a fascist impulse? The jury's out--and is likely to remain out--but it's a question worth asking.