Some world leaders live in palaces. Some enjoy perks like having a discreet butler, a fleet of yachts or a wine cellar with vintage Champagnes. Then there is José Mujica, the former guerrilla who is Uruguay's president. He lives in a run-down house on Montevideo's outskirts with no servants at all. His security detail: two plainclothes officers parked on a dirt road. In a deliberate statement to this cattle-exporting nation of 3.3 million people, Mr. Mujica, 77, shunned the opulent Suárez y Reyes presidential mansion, with its staff of 42, remaining instead in the home where he and his wife have lived for years, on a plot of land where they grow chrysanthemums for sale in local markets. His net worth upon taking office in 2010 amounted to about $1,800 the value of the 1987 Volkswagen Beetle parked in his garage. He never wears a tie and donates about 90 percent of his salary, largely to a program for expanding housing for the poor. His current brand of low-key radicalism ... exemplifies Uruguay's emergence as arguably Latin America's most socially liberal country. Under Mr. Mujica, who took office in 2010, Uruguay has drawn attention for seeking to legalize marijuana and same-sex marriage, while also enacting one of the region's most sweeping abortion rights laws and sharply boosting the use of renewable energy sources like wind and biomass. For democracy to function properly, [Mujica] argues, elected leaders should be taken down a notch. "We have done everything possible to make the presidency less venerated," Mr. Mujica said in an interview one recent morning, after preparing a serving in his kitchen of mate.