Mark Sanford and Maria Belen Chapur, in a Rare Outing, Attend Party for Argentina (Photos)

South Carolina Congressman Mark Sanford and Maria Belen Chapur, the Argentine woman for whom he gave up his marriage, and—briefly—his political career, appeared together Tuesday at a party to celebrate 30 years of democracy in Argentina. The couple, whose affair became public in 2009, were among about 200 guests at the Spanish Colonial mansion that is the century-long headquarters of the Organization of American States. They slipped in virtually unnoticed, and remained in the back of the room, for part of the program of speeches, music, and tango. The Ambassador of Argentina, Cecilia Nahon, welcomed them and stayed with them for only a brief conversation.

Sanford was South Carolina’s governor when he ostensibly went on a hiking vacation for several days, telling his staff he would be unreachable. Later he revealed he had been in Buenos Aires with Chapur, who he called his “soul mate.” The episode made national news and grew into a scandal that lit up the media and prompted his wife, Jenny, to move out of the governor’s mansion. They divorced a year later.

Sanford completed his term as governor and moved to Charleston, where he developed an interest in Buddhism* and also became a political commentator. Early this year he announced plans to run for his old House seat in a special election, which he won in May. He also became engaged to Chapur, though no wedding date has been announced. In an October television interview, Chapur said “when we’re together, we live together,” in both Charleston and Washington.

What the couple was able to enjoy during their half hour at the OAS was some of the romance of Chapur’s home country. As Maestro Sergio Buslje conducted the Pan American Symphony Orchestra, tango dancers Carolina Juarena and Didier Bravo glided, whipped, and dipped to the music. Popular Argentine singer María Volonté performed a few ballads.

Ambassador Nahon, who began the evening with welcoming remarks, recalled the history of democracy in Argentina. After the government was brought down by a military coup in 1976, the country entered, said Nahon, “seven years of darkness.” Democracy returned in 1983 with the election of Raul Alfonsin. “Today all Argentines acknowledge that democracy is the only possible form of government,” Nahon said. “This is a very special day for us.” A member of her staff read a letter from Secretary of State John Kerry and there were also remarks from the OAS’ Secretary General, Jose Miguel Insulza.

*His chief of staff stresses that his faith is Christian.

This article has been updated from a previous version.