The racist rampage in Buffalo over the weekend that claimed the lives of 10 people, most of whom were Black, has drawn attention to Carlson’s documented advocacy of the “Great Replacement”—a theory according to which immigrants and ethnic minorities gain political power to the detriment of Caucasians.

The theory, once a fringe conspiracy embraced by white supremacists, has now become more mainstream and was cited by the suspected Buffalo killer in writings before the incident.

“In a craven quest for viewers and ratings, organizations like Fox News have spent years perfecting the craft of stoking cultural grievance and political resentment that eerily mirrors the messages found in replacement theory,” Schumer said during a speech on the floor.

He also wrote directly to Rupert Murdoch and his news CEO, Suzanne Scott, copying in Carlson, to ensure the network ceases recklessly serving as a platform for the ideology.

“I urge you to take into consideration the very real impacts of the dangerous rhetoric being broadcast on your network on a nightly basis,” Schumer wrote.

During Fox Corporation’s annual spring pitch to advertisers on Monday, Carlson had limited airtime in a pre-recorded presentation — a move described as an “assiduous sidestep” in light of recent controversies by trade title Variety.

However, a spokesperson for Fox told Fortune that Carlson was never intended to feature in this upfront presentation and has not done so in previous years, given that upfronts are previews for new content and not current stars. The spokesperson pointed to comments made before the shooting that the network was focusing on “pitching scale”, as prime time has long been a ratings leader but the network is “now reaching a new level of success in certain dayparts.”

A recent investigation by the New York Times into the 1,150 episodes aired between November 2016 and the end of 2021 found that over 400 contained rhetoric related to replacement theory, while over 600 referenced anti-white bias.

Carlson mocked the story by picturing himself laughing next to the paper’s headline “American Nationalist” in a post that gained 200,000 likes.

The host also took to the airwaves on Monday to defend himself, arguing that shooter Payton Gendron thought Fox News was in fact “part of some global conspiracy against him,” in what the L.A. Times called “a dangerous new low” after effectively absolving his own show of any responsibility.

Congressman Matt Gaetz, a member of Trump’s wing of the party, has praised Carlson, as have many others, for warning Americans are in danger from immigrants who would swell the ranks of the Democrats.

The enormous popularity of Tucker Carlson Tonight has helped ensure the Fox News Channel was the most-watched U.S. network in prime time across all basic cable networks for a sixth straight year.

His ability to shape U.S. political debate was on full display in January after Republican Sen. Ted Cruz personally requested to appear on Carlson’s show to apologize after the latter accused him of aiding Democrats by calling the Capitol riots a “violent terrorist attack.”

Editor’s note: This report has been corrected to remove all references in the headline to Tucker Carlson’s involvement in Fox News’ annual upfront event and to clarify in the text the limited nature of his role at the event. Incumbent hosts such as Carlson have had limited or nonexistent roles in upfronts for years, as the events are intended to highlight new programming.