Whatever the direct damage caused by the accident at Three Mile Island nuclear plant, the political consequences for the American atomic power industry could be profound.

The Pennsylvania incident on Wednesday is the latest in a series of episodes that may undermine the years of assurances by the industry and its governmental allies that a major accident of Three Mile Island proportions could not occur.

In recent months:

Five nuclear power plants on the East Coast have been shut down because of questions about their resistance to earthquake damage.

The Nuclear Regulatory Commission repudiated the Rasmussen report, a major, government-commissioned study of atomic safety that concluded the risk of nuclear disaster is very small.

The trial opened in a suit brought by the estate of Karen Silkwood, a plutonium plant worker killed in an auto crash. In the suit, a company processing atomic fuel is accused of negligence and widespread health safety violations.

The pall cast by these events contrasts sharply with the industry's outlook as this year began. With increasing pressure for a solution to the energy problem and a growing public perception of government regulation as excessive and costly, the atomic power industry had hoped to cut back the regulations that now make the licensing of a nuclear plant an 11-year process.

But yesterday, as Three Mile Island plant's owners were saying that the reactor's safety systems in fact had prevented more serious accident, critics were citing the incident as evidence that nuclear power is too risky.

"This incident makes a lie of the soothing propaganda of the nuclear zealots that serious nuclear accidents are nearly impossible," said California Gov. Edmund G. (Jerry) Brown Jr., who has been criticized widely for stopping the Sundesert nuclear plant in his state. "I see this as a major issue in the decade ahead..."

One result of the accident, according to White House sources, is that President Carter may not include the plea for nuclear power that Energy Secretary James R. Schlesinger has been urging him to make in his coming energy message.

"If I were sitting in the president's chair, I would pause a long while before issuing any statement encouraging a rapid expansion of nuclear power-it just has to be postponed until the political clamor recedes," one high administration official said.

Reflecting on the Pennsylvania accident, Rep. Morris K. Udall (D-Ariz.) said yesterday he feels it is difficult to predict what the impact on the industry will be. Because the accident, though serious, was contained by the safety systems, it is possible that in two or three years there will be "a surge of confidence" in nuclear power, he said. On the other hand, he said, there could be the opposite reaction and "the de facto moratorium we have on new plants will continue."

The intensifying debate over nuclear power's future has come at a particularly difficult time for the industry, which is dominated by such firms as General Electric and Westinghouse. Orders for new nuclear plants, which peaked at 41 in 1973, fell to two last year.

There are a variety of reasons for the decline, including a reduction in the utilities' own estimates for future generating capacity.

But growing public opposition to nuclear power, which has led to long delays in getting plants approved and the threat of moratoriums on new plants in five states, has put the nuclear industry on the defensive.

Despite the setbacks, however, the nuclear power industry and its backers make a vigorous argument for atomic plants as a means of reducing the nation's dependence on foreign oil.

Mike Segal of the Edison Electric Institute pointed out that nuclear power provided 13 percent of the nation's electrical needs last year, displacing millions of barrels of imported oil. "The accident doesn't change in any manner our position that nuclear power is needed," Segal says.

This view is shared by Sen. Henry M. Jackson (D-Wash.) who said yesterday, "The immediate effect of the incident hurts." Chairman of the Senate Energy Committee, Jackson says that the loss of the Three Mile Island plant could increase oil imports by 45,000 barrels a day.

Dr. Norman Rasmussen of the Massachusetts Institute of Technology author of the Rasmussen report, said that based on information he had the Harrisburg accident "was not serious from the standpoint of public consequences." Rasmussen said that he expects the public impact on a short-term basis to be significant.