On Wednesday, 2020 presidential candidate Sen. Elizabeth Warren (D-MA) put up a billboard in the heart of Silicon Valley pressing for big tech companies like Facebook, Amazon, and Google to be broken up.

The billboard is located at 4th and Townsend, right next to the city’s primary Caltrain stop, where a substantial chunk of South Bay technology workers arrive each morning. It’s not exactly prime placement — considering it’s neither facing the Caltrain station nor along the most traffic’d sidewalks for employees commuting back to the South Bay — but the billboard is just blocks from the headquarters for Lyft and Dropbox, among other startups. Alongside the call for antitrust action, the billboard includes a short-code number for passersby to subscribe to updates from the Warren campaign, a common fundraising tactic. The billboard is scheduled to run until next Wednesday.

Earlier this year, Warren announced a grand proposal to break up giant tech firms, launching a discussion that was previously being held solely in academic circles into the mainstream political discourse. In her proposal, Warren suggests that companies like Facebook have become too large and powerful, and should have previously acquired assets, for example WhatsApp and Instagram, spun back off into their own companies.

Her proposal also includes a plan to pass legislation that would prohibit platform owners with more than $25 billion in revenue to participate on their platforms as well. This policy would largely affect companies like Amazon that both run a sales platform and sell their own products on the site.

“Today’s big tech companies have too much power,” a Warren aide said. “They’ve bulldozed competition, used our private information for profit, and tilted the playing field against everyone else. And in the process, they have hurt small businesses and stifled innovation. Elizabeth’s plan would help ensure tech giants do not crowd out potential competitors, smother the next generation of great tech companies, and wield so much power that they can undermine our democracy.”

Facebook, Google, Amazon, and Apple did not immediately respond to requests for comment.

Update, 4:00 PM ET: Added more context about the billboard’s placement, from a Verge editor who used to ride the Caltrain every day.