Portland Mayor Neil Goldschmidt, who was selected by President Carter yesterday to be the next secretary of transportation, was the prime mover behind a downtown Portland renovation project that used transit to help revive the center city.

Goldschmidt would be the first secretary of transportation with a strong transit background at a time when mass transit programs are seen as part of the solution to the nation's energy problems.

Beyond that, Goldschmidt, 39, is described by acquaintances as a top-notch administrator and an energetic man who is capable of grasping issues quickly.

"This guy is the brightest, most persuasive, most dominant politician I've ever known," said Louis Scherzer, executive vice president of a Portland savings and loan. "He never runs down. He'll be far more effective in a Cabinet seat than he would in the House or the Senate."

Goldschmidt, a fifth-generation Oregonian, received his law degree from the University of California at Berkeley. He ran for city council in Portland in 1971, then for mayor in 1972. He was reelected in 1976, winning the six-candidate primary with 53 percent of the vote. He had no opponent in the general election. He was an early supporter of Jimmy Carter's presidential aspirations.

When he took the mayor's office in 1972, one of the long-raging controversies in that city was whether to build two interstate highways through Portland, with one of them going to spectacular Mt. Hood east of the city.

Both of the highway projects were canceled and, with the help of changes in the federal highway law in 1974, much of the money that would have been spent to build them was released for use on other transportation-related projects.

Portland's Transit Mall was one of the results. Two parallel business streets through the Portland core were closed to all but buses and pedestrians. Sidewalks were widened, trees were planted and buses were rerouted so that every line in Portland would come down those two streets.

"Goldschmidt was bucking both business and labor on that proposal," Scherzer said, "but the energy situation has proven him correct." The Transit Mall also has been a business success. Downtown department stores have been spruced up, and a major retailer is building a five-block development along the mall.

Portland also is well along with the planning of a trolley system that will connect downtown and the mall with some Portland suburbs. Interstate highway funds will support that program, too.

Officials at the U.S. Conference of Mayors yesterday were ecstatic. John Gunther, executive director, said that the appointments of Goldschmidt and former New Orleans Mayor Moon Landrieu to the Department of Housing and Urban Development "doubles the number of mayors who have been appointed to Cabinet posts since the New Deal began in 1933." CAPTION: Picture, Goldschmidt, now serving as mayor of Portland, Ore., meets with President Carter at the White House. White House Photo