SAN FRANCISCO — When Christine Blasey Ford testified before Congress last month about Justice Brett M. Kavanaugh’s alleged sexual assault, a website called Right Wing News sprang into action on Facebook.

The conservative site, run by the blogger John Hawkins, had created a series of Facebook pages and accounts over the last year under many names, according to Facebook.

After Dr. Blasey testified, Right Wing News posted several false stories about her — including the suggestion that her lawyers were being bribed by Democrats — and then used the network of Facebook pages and accounts to share the pieces so that they proliferated online quickly, social media researchers said.

The result was a real-time spreading of disinformation started by Americans, for Americans.

What Right Wing News did was part of a shift in the flow of online disinformation, falsehoods meant to mislead and inflame. In 2016, before the presidential election, state-backed Russian operatives exploited Facebook and Twitter to sway voters in the United States with divisive messages. Now, weeks before the midterm elections on Nov. 6, such influence campaigns are increasingly a domestic phenomenon fomented by Americans on the left and the right.