Libby DePiero once drove her Ford Focus so far to attend a Trump campaign rally—about 1,000 miles from her home in Connecticut to Indiana—that when she lay in bed that night she thought the twitching in her driving leg was coming from an animal under the mattress.

The 64-year-old retiree, who prefers sparkly nail polish, leopard prints and selfies with Trump campaign officials, is almost always one of the first few people in line at the president’s campaign events, part of the self-described group of “Front Row Joes” who routinely travel to see the president perform. Several, like Ms. DePiero, have attended more than 50 Trump rallies.

She keeps going because she trusts only the president to deliver her the news. “How else would I know what’s going on?” she said.

Mr. Trump has hosted more than 550 ticketed campaign events since 2015, at least 70% of which include his trademark rallies, according to Republican officials. These rallies form the core of one of the most steadfast political movements in modern American political history, a dynamic that has reordered the Republican Party.

Mr. Trump’s perpetual tour attracts a coterie of political pilgrims who travel across the country and encamp outside arenas for days at a time for the chance to stand in the front row and, for 90 minutes, cheer the man they say has changed the U.S. and, in many cases, their own lives. Somewhere between 5% to 10% of attendees have been to multiple events, the officials said.