WASHINGTON (AP) — President Donald Trump escalated his war on social media companies Thursday, signing an executive order challenging the liability protections that have served as a bedrock for unfettered speech on the internet.

Still, the move appears to be more about politics than substance, as the president aims to rally supporters after he lashed out at Twitter for applying fact checks to two of his tweets.

Trump said the fact checks were "editorial decisions" by Twitter and amounted to political activism. He said it should cost those companies their protection from lawsuits for what is po...