NEW YORK, NY.- Marc Pachter, who transformed the National Portrait Gallery in Washington from a collection primarily of solemn paintings of old white men into a more up-to-date museum that now includes illustrations and interviews with diverse living luminaries, died Feb. 17 in Bangkok. He was 80.

The cause was cardiac arrest, his son, Adam, said. Pachter, who lived in New York City, died in a hospital while vacationing in Thailand.

As director of the Portrait Gallery from 2000 to 2007, Pachter presided over a $300 million renovation that re-imagined the museum while maintaining its artistic integrity.

In 2001, he was instrumental in guaranteeing that Gilbert Stuart’s famous and unique 1796 painting of President George Washington — known as the Lansdowne Portrait, after one of its earliest owners, the first Marquess of Lansdowne in England — would remain in the nation’s capital for public display instead of being auctioned off by its latter-day owners, as was threatened.

“If there is an American icon, this is it,” Pachter said in 2001.

The life-size painting depicts the president urging Congress to adopt the unpopular Jay Treaty, which resolved the new nation’s remaining issues with Britain. Washington posed in person for the head and face. Stuart made three copies of the full-figure painting — one of which hangs in the White House — and five other versions.

The painting was lent to the Portrait Gallery in 1968 by its owners at the time, who lived in Britain. But in 2001, they arranged to auction it off at Sotheby’s — unless the gallery ponied up $20 million.

When Pachter publicly appealed for funding, a Las Vegas foundation established by Donald W. Reynolds, a media mogul, stepped up. It donated the $20 million to purchase the painting for the gallery’s permanent collection, another $6 million to underwrite its exhibition on a national tour, and $4 million for renovations so that it could be properly displayed.

Pachter also notably revoked a gallery policy requiring that subjects of portraits be dead for at least 10 years, bringing the collection into the 21st century.

But Pachter often said he was proudest of another innovation, what he called “living self-portraits” — his probing interviews of prominent cultural figures before a live audience.

He began an interview of Steve Martin by remarking, “It is said that all comedians have unhappy childhoods. Was yours unhappy?” To which Martin parried, “What was your childhood like?”

“And I said,” Pachter recalled, “‘My father was loving and supportive, which is why I’m not funny.’ And he looked at me, and then we heard the big, sad story.”

Pachter’s expertise was in political science and history, which attracted him to the Smithsonian and got him promoted there. Lonnie Bunch III, the secretary of the Smithsonian Institution, which oversees the Portrait Gallery, described Pachter as “a gifted scholar and visionary historian.”

“It’s very instructive,” Adam Pachter said of his father, “that his title had nothing to do with art, and even when he rose to run the National Portrait Gallery, he was always most interested in what portraits said about the times and people they depicted, rather than the brushstrokes.”

Marc Jay Pachter was born on May 7, 1943, in the New York City borough of the Bronx to Jack and Ferle (Greenfield) Pachter. His family moved to California when he was a year old after his mother was diagnosed with multiple sclerosis. His father had been trained as a lawyer, but after his wife took ill he opened a five-and-dime store in Gardena, east of Manhattan Beach, to earn money more quickly, family members said.

Pachter graduated from the University of California, Berkeley, with a bachelor’s degree in political science in 1964. Without ever having taken a history course, he said, he was accepted in a doctoral program at Harvard as a Woodrow Wilson Fellow and a Five-Year Prize Fellow in American History.

The Portrait Gallery hired him in 1974, after he had completed his master’s degree. (He never received a doctorate.) His first exhibit, “Abroad in America,” proved so successful that he was hired to be the gallery’s chief historian, setting him on a three-decade career with the Smithsonian Institution.

Along the way he chaired the Smithsonian’s 150th anniversary celebration in 1996, served as the Smithsonian’s deputy assistant secretary for external affairs, led the Portrait Gallery from 2000 until his retirement in 2007, then came out of retirement to be acting director of the Smithsonian’s National Museum of American History, from 2011 to 2012. It was his second stint as acting director of the museum; he had served in that capacity from 2001 to 2002 as well, becoming the first Smithsonian official to hold two directorships simultaneously.

Pachter’s marriage to Elise Forbes ended in divorce in 1989. In addition to their son, Adam, his survivors include a daughter, Gillian; his sisters, Sharon Elstein and Beverly Beckman; and four grandchildren.

Pachter edited several books, including “Abroad in America: Visitors to a New Nation, 1776-1914” (1976), “Champions of American Sport” (1981) and “Telling Lives: The Biographer’s Art” (1979), which was inspired by a conference on biography that he organized.

A biography, he told Brian Lamb in an interview on C-SPAN in 2007, is “written by an immodest person because the notion that you can understand another person’s life is preposterous.”

He added, “So a biographer looks back and decides, ‘I’m going to impose a shape on this life which is deeper and more important a meaning for life than the individual would have guessed.’”

When Pachter retired, the National Portrait Gallery commissioned a portrait of him, painted by Robert Liberace. It hangs in his Upper East Side apartment. With his death, his family hasn’t yet decided precisely where the painting will now go, but Adam Pachter said he was confident that “it will hang in a place my dad loved to hang out.”

“A bar in a museum would be a pretty spot-on place for my dad,” he added, “sipping drinks named for famous Americans.”

This article originally appeared in The New York Times.