Noting Limbaugh’s success, radio executives started hiring conservative hosts—first local personalities, and then later national names like G. Gordon Liddy and Michael Reagan—to fill time slots on an expanding number of talk stations.

Read: Rush Limbaugh doesn’t know he’s part of the establishment

Although leading Republicans were slow to catch on to the political potential of the medium, by the mid-1990s, talk radio was an integral element of GOP communications strategies. It provided a boost for Republicans as they pushed to enact an agenda and worked to win elections. Republicans, including House Speaker Newt Gingrich, pumped information to hosts, chatted with them regularly, and generally saw talk radio as an ideal way to reach their base with a message and learn how voters around the country felt about key issues.

Many on the left surmised that the hosts were puppets, plugging whichever policies Gingrich and others wanted them to. But selling the GOP message was never the hosts’ top priority. In my research into the history of conservative talk radio, the executives, producers, and hosts whom I interviewed told me over and over that their main goal was to produce the best radio show each day, one that could command the largest audience possible that tuned in for the longest possible time.

Over time, this focus on the commercial imperatives of AM radio would transform politics. To keep audiences engaged and entertained, hosts grew more and more strident as the years passed, depicting politics as warfare—and started targeting moderates in the Republican Party.

In its early phases, conservative talk radio had exhibited a pragmatic streak that would sound foreign today. In 1994, Limbaugh cautioned against single- issue voting. He advised television viewers—he had a TV program from 1992 to 1996—not to oppose Mitt Romney, the Republican then running as a moderate against the liberal senator Ted Kennedy in Massachusetts. As Limbaugh explained, electing Romney, despite his lack of conservative fervor, would be a step “in the right direction.”

Hosts never loved moderates, and never hesitated to criticize them for actions out of step with hosts’ vision for the country. But they understood that such figures were crucial to securing a majority, without which their preferred agenda had no shot.

But this detente started to break down as the 2000s progressed. In one 2005 harangue prompted by Republicans who voted against oil drilling in the Arctic National Wildlife Refuge, Limbaugh declared, “There’s no such thing as a moderate. A moderate is just a liberal disguise, and they are doing everything they can to derail the conservative agenda.” He deemed such behavior “unacceptable” and read listeners the names of those Republicans voting no. Even so, Limbaugh still crucially refrained from calling for those Republicans to lose.