With Americans going to the polls on Tuesday, it is down to the wire for social media companies to show that they have clamped down on disinformation and foreign interference through their sites. The companies want to prove that the midterm elections will not be a repeat of 2016, when Russian operatives used Facebook, Twitter and YouTube to spread divisive messages in an attempt to influence how the American electorate voted.

Facebook, which has borne the brunt of scrutiny over election interference, has introduced measures to limit who can buy political ads, has hired more people to monitor what gets posted, and has constructed a “war room” to root out false information and stop it from spreading. Last week, Facebook’s chief executive, Mark Zuckerberg, told investors that the company was getting “better and better” at detecting election interference but that “there are going to be things that our systems miss no matter how well tuned we are.”

A close look at Twitter also suggests that disinformation and election interference are far from under control. Even as the company has taken steps to reduce problems, new instances of misinformation campaigns continue to surface.

“Our work on this issue is not done, nor will it ever be,” Jack Dorsey, Twitter’s chief executive, told Congress in September. He said that the company had learned valuable lessons since the 2016 election and that it was now removing 214 percent more accounts a year for violating its policies against manipulation.

[Here’s a guide to everything you need to know about the November elections.]

Twitter began looking more closely at election interference after the 2016 presidential vote. Late that year, it assembled a data science team to use technology to detect malicious and misleading behavior on its service. In particular, the team tries to identify oddities, like a cluster of accounts that were registered with the same email address or phone number, or accounts that were engaging in spammy behavior like tweeting constantly at high-profile accounts to amplify their posts.

