Twitter will ban all political advertising worldwide, CEO Jack Dorsey tweeted on Thursday, citing challenges such as machine learning optimization, micro-targeting, and deep fakes. The ban will come to effect on November 22.

One day after rival Facebook agreed to pay £500,000 pounds over the transatlantic Cambridge Analytica scandal, it social media rival divides the political market ahead of the 2020 US elections. On Thursday, Facebook founder Mark Zuckerberg defended his company’s policy, suggesting that it is not up to private companies “to censor politicians or the news.”

US campaigns are expected to pay $6bn for online advertising. Twitter’s stock lost 1,9% following the announcement.

Facebook has made a decision to not fact-check ads run by politicians running in 2020. In response, Democratic candidate Elisabeth Warren run a false campaign on Facebook suggesting that Zuckerberg had personally endorsed President Trump for reelection.

The news was dismissed by US President Donald Trump’s manager Brad Parscale as an attempt by the left to silence the conservatives. President Trump said Twitter’s decision was “dump” as the platform walked away from millions of dollars in revenue.

The move was hailed by Joe Biden’s spokesman, Bill Russo, as a victory for “the integrity of our democracy.” Hillary Clinton also welcomed Twitter’s ban and called on Facebook to review its position.