WASHINGTON — As he opened an event that had brought 200 conservative social media firebrands to the White House, President Trump wanted his guests to know just how much he appreciated their work helping shape the online narrative about his presidency and a re-election fight.

“The crap you think of,” Mr. Trump said as he surveyed his Twitter kingdom, “is unbelievable.”

Mr. Trump was once an outsider political candidate who prided himself on bending rules and subverting norms, and he wants to keep that sensibility as a candidate in 2020. So on Thursday, the president went in search of outside-the-box campaign ideas from a group that also has little use for playing by the rules.

Sandwiched between a flurry of morning presidential tweets and bleeding into Mr. Trump’s early evening news conference on how his administration would collect data on citizenship, the White House Social Media Summit was dominated by activists willing to share unverified smears against Democratic presidential candidates, disseminate QAnon conspiracy theories and create memes the president might share.

“Earlier this year, the White House launched a tool to allow Americans, regardless of their political views, to share how they have been affected by bias online,” Judd Deere, a White House spokesman, said in an email explaining the origins of the event. “After receiving thousands of responses, the president wants to engage directly with these digital leaders in a discussion on the power of social media.”