COTTONWOOD HEIGHTS, Utah—A crowd of about a thousand people, dominated by opponents of President Donald Trump’s agenda, packed a raucous town-hall event here in the latest example of increased activism targeting Republican members of Congress.

Five-term Rep. Jason Chaffetz won his most recent race by nearly 50 points, but returned to his home district to find himself confronted by a sign-waving, heckling and booing chorus.

Town halls held by Republican Reps. Diane Black of Tennessee and Justin Amash of Michigan on Thursday also drew big numbers and tough questions. At earlier home-district events in states including Colorado, Florida, Virginia and California, GOP House members were surprised by rowdy crowds, often declaring support for the Affordable Care Act, which Republicans have vowed to repeal.

The protests, some organized by activists, recall the opposition early in the Obama administration to that same Democratic-sponsored health-care law. That gave birth to the tea-party movement—a parallel not lost on some protesters.

“This is our version of the tea party, and we’re not going away,” said Chris Brunelli, a Salt Lake City resident at the Chaffetz event, held at a high school in this upscale suburb.