Edward M. Kennedy took a look back yesterday at his victory in the Pennsylvania primary and pronounced himself half-satisfied.

The Pennsylvania voting, Kennedy said, indicated that half of his message -- the contention that President Carter and his policies are responsible for current economic problems -- has gotten through to voters. But he seemed to agree that the electorate has not yet accepted the other essential plank of the Kennedy candidacy -- that Kennedy and his policies would be better.

Which means, he said, that his underdog campaign will just keep on keeping on. "We're going to see a lot of auto plants and eat a lot of tacos," Kennedy said, indicating lots of activity over the next five weeks in states like Ohio and Michigan, Texas and California.

At a breakfast with reporters yesterday, Kennedy looked candidly at his Pennsyvlania campaign. He also pledged, as he has after every other primary this year, to continue his battle against Carter until the day ballots are cast at the Democratic convention.

As Kennedy sees it, the most satisfactory conclusion to be drawn from Pennsylvania is that Democrats are no longer willing to excuse Carter for the nation's economic difficulties. "They do hold him accountable now, and that's right -- they ought to reject him," Kennedy said.

Kennedy indicated that perhaps the most annoying aspect of this campaign -- more annoying, even, than the recurring "character" issue -- is the suggestion, raised by Carter and reflected widely in opinion surveys, that no president could do much to handle inflation and other economic ills.

For a member of the Kennedy family, whose entire political creed pivots on the assumption that government can solve national problems, that very idea is anathema.

But Kennedy said yesterday that, even if people now agree that "a president can make a difference," they may not be ready to acknowledge that a President Kennedy would make the difference.

"What we really have to do now," he said, "is to tie that into a message where we say, look, there is something that can be done and if Kennedy is elected these are the kinds of things that can be done.

"And that's an evolutionary thing. That's something that takes time . . . We're looking for more effective ways of getting that across."

Kennedy starts a week-long trek today through five states with a side trip to Mexico City, where he will meet with Mexican President Jose Lopez Portillo and, presumably, get some television coverage that will help him with Hispanic voters in California and Texas.

The candidate and his campaign manager, Stephen Smith, say that the campaign is in better shape financially than it has been in months. Its net debt is down to about $300,000 from about $1 million in February, Smith said. And that could be eliminated through sales of original art works donated to the campaign by Andy Warhol, Robert Rauschenberg, and Jamie Wyeth, he added. Meanwhile, according to Smith, contributions are still coming in at a fairly steady rate of a quarter-million dollars per week.

None of that, though, makes up for Carter's big lead in delegates won. Kennedy still has to hope for major defections by the president's erstwhile supporters. "People have to sense," Kennedy said, "that it's over for Jimmy Carter."