SAN FRANCISCO – As voters headed to the polls on Election Day, social media companies scoured their platforms for any content that would deter them.

Facebook said it swiftly removed misinformation, such as posts and memes urging Republicans and Democrats to vote on the wrong day and claims that federal immigration agents would be patrolling polling places.

In recent days, Twitter cracked down on a rumor that Immigration and Customs Enforcement agents would check voters' citizenship at the polls and deport anyone in the country illegally and deleted more than 10,000 automated accounts posting messages claiming to be from Democrats that discouraged people from voting in Tuesday's election.

The stakes could not be higher for Facebook and Twitter after Russian operatives targeted African-American, Hispanic and LGBT voters with false voting information. If social media companies can't clamp down on the spread of misleading information during elections, lawmakers have threatened regulation.

Yet falsehoods continued to spread Tuesday. Two busloads of "illegals" were paid to vote for Texas Senator Ted Cruz's challenger Beto O'Rourke. Not true. Florida gubernatorial candidate Andrew Gillum's siblings were charged with voter fraud. Also not true. Early voting numbers are in from Michigan. There is no early voting period in Michigan. BuzzFeed busted a fake Donald Trump Twitter account with more than 10,000 followers which had been spreading Election Day hoaxes.

USA TODAY also found Twitter posts, some directing Republicans to vote on Nov. 7, others directing Democrats to cast their ballots a day late, but most of the misinformation appeared to have very limited reach and to be relatively harmless.

Still, researchers are alarmed by misleading information and outright fabrication on social media. New research from Oxford University’s Computational Propaganda Project found that "junk news" is spreading more widely on social media in this election cycle than it did two years ago. And Columbia University's Jonathan Albright has warned in a series of essays on Medium that disinformation on social media in 2018 is more pervasive than it was two years ago.

Under pressure to better police their platforms, social media companies are scrambling to prove that the 2018 midterms will not be a repeat of the 2016 presidential election, when false information about voting proliferated quickly, boosted by foreign governments and rogue bad actors closer to home.

Facebook and Twitter have added more staff and strengthened automated systems to monitor misinformation. And they are working closely with the Department of Homeland Security and other federal officials.

Election officials and voting rights advocates are alerting social media companies to any efforts that could depress turnout, such as voters being erroneously told they can submit their ballot choices via text message.

Much of the misinformation appears to be coming from Americans, not from foreigners, according to research from Harvard’s Shorenstein Center on Media, Politics and Public Policy.

Last month, Facebook said it removed hundreds of U.S.-based pages and accounts peddling what the company called "sensational political content" spanning the political spectrum, from Right Wing News to the left-leaning Reverb Press. It also broadened its ban on misinformation to include how people can vote or whether their vote will count.

"Every election there are those out there who try to send information to mislead or otherwise confuse voters. Those have been rapidly addressed by the platforms," a Department of Homeland Security official said Tuesday. "No tie back to any foreign actors that we have seen."

That's not to say that Russian operatives are sitting out the midterms. Reuters reported Tuesday that Russian agents with ties to the government have just been doing a better job of covering their tracks as they spread divisive content.

On Monday night, Facebook disclosed that it had removed more than 100 accounts – 30 on Facebook, 85 on Instagram – engaging in coordinated activity in French, English and Russian on a tip from law enforcement, raising the possibility that foreign actors were trying to meddle in a U.S. election on the eve of the midterms.

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