Even for a campaign creating regular media tremors, the hiring of Stephen K. Bannon as the new campaign C.E.O. for Donald Trump has to count as a real shock. Trump is a first-time candidate who has talked about professionalizing his campaign, and yet he has hired a media bomb-thrower with no experience on the trail. But on another level, it is no surprise, since for years there has been a political symbiosis between Trump, Bannon, and Breitbart Media, the news organization that Bannon has led for the last four years. In truth, Bannon and Breitbart Media were Trump before Trump, creating the political philosophy and the political army in waiting that has been the engine for the candidate’s astonishing rise in American politics.

To understand the relationship between Trump and Bannon, you need to start with Andrew Breitbart himself. Over a short, fireworks-laced career, Breitbart helped re-write the rules of political discourse in the U.S. Starting in 2007, after a stint at the Drudge Report, he launched a series of Web sites—Big Hollywood, Big Government, and Big Journalism, all under the Breitbart.com umbrella—to challenge the narratives set forth by so-called “liberal media” institutions. His sites, really a decentralized blogger network, were threaded together by furious denunciations of government, politicians, journalists, and Democrats, and they were fueled not by traditional norms of journalism, but largely by anger. It was a potent audience that might, in particular hands, serve as a potent electorate.

Indeed, Breitbart has given voice to millions of mostly working-class white voters who are anguished over the loss of status, the loss of certainty, and the diminishment of a long-cherished way of life—and who tend to blame Congress, the mainstream media, big business, and the Republican establishment for these misgivings. As The New Yorker graphically described it, Breitbart and his fellow bloggers and aggregators were not content providers, but “malcontent” providers—“giving seething, sneering voice to what he characterizes as a silenced majority.” Breitbart himself would not have disagreed. “I like to call someone a raving cunt every now and then,” he told the magazine, “when it’s appropriate, for effect.”

Breitbart unexpectedly died of heart failure, in 2012, at the age of 43, but the movement that set his media company in motion did not end with his death. Perhaps more than any other outlet, Breitbart, which notched 13.8 million unique visitors in June, according to ComScore, has built an audience that has indeed become the foot soldiers, or electorate, for Donald Trump. The connection between Breitbart and Trump is so strong that many refer to the site as “Trumpbart.” In fact, the company, over the strong objections of some of its staff, chose to side with the Trump camp over its own reporter earlier this year when Trump’s campaign manager, Corey Lewandowski, grabbed Breitbart reporter Michelle Fields at an event in Florida. (Fields declined a request to comment for this story. Charges have since been dropped.)

Video: Donald Trump and the R.N.C.

In the wake of Andrew Breitbart’s death, Bannon quickly grabbed the reins of power and he continued to build the network in the spirit of its founder. He is likely the most potent conservative news executive in a post–Roger Ailes landscape, and his new role as campaign C.E.O. overshadows even Ailes’s reported role as a Trump adviser, which The New York Times revealed this week. (Trump spokesperson Hope Hicks has denied this relationship.)