On Friday, three days after Rep. Herbert E. Harris II (D-Va.) said that President Carter should "consider stepping down," the White House distributed a photograph showing the two men effusively smiling as if nothing had happened.

"Are you certain it's Herb Harris in the photograph?" asked assistant White House press secretary Richard Nelson yesterday.Both Carter and Harris spokesmen were at a loss to explain why Harris, who said Tuesday he was no longer supporting the president's reelection, was used in a picture designed to show unity among delegates to the Democratic National Convention.

Family members at Harris' Mount Vernon home said yesterday that the congressman was on vacation and could not be reached.

The White House photograph, distributed nationally by the Associated Press, made the front page of yesterday's New York Times and prompted a number of calls to the White House.

"It doesn't strike me as being unusual," said Carter aide Nelson at first.

"Well, there were a limited number of shots to choose from," he said. "It was probably the best picture we had. It was the only one we distributed."

Nelson said that Harris was one of 73 "staunch" Carter supporters from the House of Representatives who met with the president Friday where Carter said that an open convention would be a "travesty."

Harris also said Tuesday that he is against moves by about three dozen House Democrats to "dump Carter" and force an open convention. But he said he thought Vice President Mondale or Secretary of State Edmund Muskie would make a better presidential candidate than Carter.