election season. >> and brine stelter shows us, they may have been read and believed by millions of voters. >> reporter: did the spread of fake news on the web help elect donald trump? we may never know for sure, but researchers are asking the question because made up, false stories are polluting people's facebook timelines and twitter streams. >> this cesspool of nonsense -- >> bogus stories. >> reporter: and getting worse. even president obama is raising the alarm. >> if we are not serious about facts and what's true and what's not, then we have problems. >> reporter: these problems are not brand new. they're becoming a lot more prevalent. here is an example, a story claiming a protester was paid $3,500 to make trouble at a trump rally. this went viral during the campaign. it looked like an abc news story, but the url reveals it's