Google and Twitter are applying pressure to Facebook in a big way. In the last three weeks — as the Iowa caucus looms just months away — both platforms have restricted political advertising on their services.

Now, after standing by its policies, Facebook’s advertising brain trust is huddling to consider changes to its rules on political advertising, including ad targeting restrictions of its own. In a statement to BuzzFeed News provided before Google made its announcement, a Facebook spokesperson was definitive: “Nothing is off the table.”

Political advertising professionals and tech industry sources said Google’s move — which limits political ad targeting criteria to age, gender, zip code, and context — puts the onus on Facebook to act. Many worried it would push Facebook to roll out draconian restrictions, hampering their ability to get their message across on what they said was the most important online advertising platform.

“Twitter fired the starting gun. Google put the weight of the ocean on them,” Eric Wilson, a Republican digital strategist, told BuzzFeed News. “The pressure is really on Facebook to do something, to make a change. I hope they make a good, informed choice.”

“Twitter fired the starting gun. Google put the weight of the ocean on them.”

Facebook did not respond to a request for comment.

Jenna Golden, a former Twitter employee and now the president of Golden Strategies, a political advertising consultancy that works with news publishers, expressed a similar sentiment. “No doubt it puts pressure on Facebook,” she told BuzzFeed News, “but Facebook has generally taken a more hands-off approach than other platforms throughout this process.”

Should Facebook follow Google’s lead, Golden said, the impact would be substantial — and “catastrophic for candidates and causes.” She added: “Facebook is ground zero for cultivating a following, courting donors, and moving political programs forward. The industry spends the majority of their digital budgets on Facebook, and limiting targeting or cutting off these capabilities could cripple the ability for a new or unknown candidate or group to get on the map.”

With little oversight from the federal government, Facebook, Google, and Twitter are largely on their own when it comes to these decisions. But should Facebook make a Google-esque move, some think it would compel the government to make some rules.

“If Facebook decides to implement additional restrictions, I think legislators will finally consider implementing a comprehensive digital ad bill that addresses many of these issues,” Nick DeSarno, director of digital and policy communications at the Public Affairs Council, told BuzzFeed News. “But that won’t get done before 2020.”