In this predominantly white region of central Minnesota, the influx of Somalis, most of whom are Muslim, has spurred the sort of demographic and cultural shifts that President Trump and right-wing conservatives have stoked fears about for years. The resettlement has divided many politically active residents of St. Cloud, with some saying they welcome the migrants.

But for others, the changes have fueled talk about “white replacement,” a racist conspiracy theory tied to the declining birthrates of white Americans that has spread in far-right circles and online chat rooms and is now surfacing in some communities.

“If we start changing our way of life to accommodate where they came from, guess what happens to our country?” said Liz Baklaich, a member of C-Cubed who unsuccessfully ran for St. Cloud City Council last year. She carries an annotated Quran in her purse. “If our country becomes like Somalia, there is nowhere for us to go.”…

“I think of America, the great assimilator, as a rubber band, but with this — we’re at the breaking point,” Ms. Crockett said. “These aren’t people coming from Norway, let’s put it that way. These people are very visible.”