WASHINGTON—Chiefs of the largest social-media companies tangled with U.S. senators over their role in public discourse six days before the end of an election that has made them the target of criticism across the political spectrum.
Facebook Inc. Chief Executive Mark Zuckerberg, Twitter Inc. CEO Jack Dorsey and Sundar Pichai, CEO of Google and YouTube owner Alphabet Inc. have spent the years since the 2016 election rewriting their policies and taking a more active role in moderating online speech—in part to avoid a spotlight…