WASHINGTON (Reuters) - In his first 100 days in office, Donald Trump made fewer appearances outside of the presidential bubble than his three immediate predecessors, venturing less beyond the White House or his private Mar-a-Lago estate, according to a Reuters review. The U.S. president cast himself during his election campaign last year as a Washington outsider and a populist champion, and often seemed most comfortable at raucous campaign rallies. Trump still constantly tells Americans what is on his mind through prolific use of Twitter messages, but he has not traveled out into the country often since taking office on Jan. 20.  Trump made comments at official appearances 132 times in the first 100 days, compared with 139 by Barack Obama in the same period, 177 by George W. Bush and 162 by Bill Clinton. (tmsnrt.rs/2p8M8EU) Some 22 of his appearances were in settings other than the White House, Air Force One, a government agency or at Mar-a-Lago, a Florida resort that his administration has called the “winter White House.” That compares to 62 such appearances by Obama in his first 100 days, 80 for Bush and 46 for Clinton. Reuters reviewed public remarks delivered by the presidents using White House websites, pool reports and documents archived by the American Presidency Project at the University of California, Santa Barbara.  Trump made public comments on five separate occasions at Mar-a-Lago. None of the other three presidents spoke to the public from a personal residence during their first 100 days, although Bush spoke twice at Camp David, the rustic presidential retreat in Maryland.     Asked about his travel, Trump’s advisers say he is focused on implementing the promises he made at his campaign rallies.     “There is obviously a premium on his time,” said White House spokeswoman Natalie Strom. “We proceed with any additional travel very thoughtfully.”     Bradley Blakeman, who was deputy assistant for scheduling and appointments under Bush, said Trump may be missing out on opportunities to sell his message to the public.  “Deals are made in Washington on Pennsylvania Avenue, but they are sold on Main Street, USA,” Blakeman said. “It’s an important part of the bully pulpit.”     He said Trump should do targeted events focused on specific legislative priorities that will get coverage by local news outlets, where stories on presidential visits tend to be more positive than in the national media.     During his first 100 days, Bush visited more than half a dozen schools in Washington and at least five different states as he promoted his education initiative, No Child Left Behind.      Trump’s first major legislative push has focused on reforming the U.S. healthcare system, but he has not yet delivered remarks at a medical facility. In an interview with Reuters last week, Trump lamented the confining nature of the presidency with its 24-hour Secret Service protection. “You’re really into your own little cocoon, because you have such massive protection that you really can’t go anywhere,” he said. Still, he remains a constant focus of public attention, helped by his use of Twitter, a tool that was seldom used or was entirely unavailable to his most recent three predecessors. “Interaction online does not completely replace the value of in-person appearances, but you can’t ignore the fact that there is no limit on the amount of people the president’s tweets can reach,” Strom said. Larry Jacobs, director of the Center for the Study of Politics and Governance at the University of Minnesota, said that while Trump’s use of social media had opened a new chapter in presidential communication, his lack of sustained attention on any one issue undercut his message.     “There’s not a focus there. When a president is all over the map, then he loses his power,” Jacobs said. 