President Jair Bolsonaro of Brazil is temporarily banning social media companies from removing certain content, including his claims that the only way he’ll lose next year’s elections is if the vote is rigged — one of the most significant steps by a democratically elected leader to control what can be said on the Internet.

The new social media rules, issued this week and effective immediately, appear to be the first time a national government has stopped Internet companies from taking down content that violates their rules, according to Internet law experts and officials at tech companies. And they come at a precarious moment for Brazil.

Bolsonaro has used social media as a megaphone to build his political movement and make it to the President’s office. Now, with polls showing he would lose the presidential elections if they were held today, he is using sites like Facebook, Twitter and YouTube to try to undermine the legitimacy of the vote.

On Tuesday, Bolsonaro repeated his claims about the election to thousands of supporters in two cities as part of nationwide demonstrations on Brazil’s Independence Day.