The political powerhouse that Charlie Kirk built reached conservative college students on campuses all over the country. So when Mr. Kirk was shot and killed Wednesday at Utah Valley University, national attention turned, as it often has in tumultuous times, to the American university.

Colleges have often been the setting for America’s most divisive and memorable cultural flashpoints, over Communism and racism, the Vietnam War and the Israeli-Palestinian conflict. Throughout, they have also been the trustees of American innovation and economic promise.

But after Mr. Kirk started Turning Point USA in 2012, at age 18, to spotlight what he saw as leftism running amok on college campuses, that began to change. Mr. Kirk’s rising influence corresponded with a sharp drop in the confidence that Americans have in their universities.

The idea that liberal ideas dominate college campuses led to the modern conservative movement, after a then-unknown William F. Buckley Jr. chronicled what he described as the anti-Christian and pro-collectivism views of the Yale faculty, in the 1951 book “God and Man at Yale.”

After Mr. Kirk founded Turning Point USA, the broader political winds began changing against colleges. The group, which hosted campus events and created a national network of young Republicans, even funding conservative student government candidates, pushed the idea that colleges were becoming too liberal. The idea would eventually gain traction beyond Republicans.

Books like “The Coddling of the American Mind,” which described Generation Z as quick to censor political opponents, and which criticized university administrators for encouraging such behavior, was published in 2018 and became a best seller. Moderate, not just conservative, professors began forming groups to denounce liberal groupthink.