His spirits high and his energy unflagging, Sen. Edward M. Kennedy crisscrossed Pennsylvania this weekend with a traveling road show that often seemed long on laughs and somewhat shorter on substance.

Kennedy has no clearer idea than any of the other politicians and media "experts" here about what will happen in Tuesday's Democratic primary. But he knows that a victory here is essential for his underdog effort, and is thus driving himself in his effort to cover this big state.

By some traditional standards, he would seem to be doing well. Big crowds -- the biggest, day-in and day-out, of his six-month campaign -- have responded with outbursts of laughter and applause to his stump speech.

But then, Kennedy drew large appreciative crowds three weeks ago just before the Wisconsin primary and he was clobbered there.

The speech Pennsylvanians are cheering has evolved into a series of scornful jokes and carefully honed lines ridiculing President Carter's economic policies, campaign tactics and attitudes about government.

Kennedy invariably notes that, when Carter decontrolled gas and oil prices, the president said this would provide oil companies more money for exploration.

"But what did Mobil Oil do with its windfall profits?" Kennedy roars. "They went out and bought Montgomery Ward department store. And I ask you, how much oil do you think they'll find drilling in the aisles of Montgomery Ward's department store?"

Then the challenger moves on to some scornful comments on Carter's Rose Garden strategy. "We saw some Carter supporters outside when we came to our rally here," he says. "And we invited them in," he goes on, his voice growing to a shout, "because they don't have any rallies of their own to go to." This line generally draws a loud response from Kennedy partisans.

Kennedy likes to tell audiences about federal grants the Carter administration has directed into primary states during the election season. "We call 'em the Kennedy Challenge Grants," he laughs. "Kennedy comes into a town and gives a speech, and a few days later the mayor finds out he's getting a couple of million in some federal grant from the Carter administration.

And then there is the "Lady Macbeth scene in the stump speech, in which Kennedy makes fun of Carter's suggestions no one could solve all the problems America faces.

"I'm tired, tired of all this handwringing, handwringing," Kennedy says, wringing his hands like Lady Macbeth trying to remove the spot. "If politicians would stop this handwringing, the American people could go out and get the jobs done."

Amid all the scorn and wry humor, much of the specific, issue-oriented language that marked Kennedy's speeches two months ago has been lost. He lost mentions, for example, his proposal for gasoline rationing -- a point he discussed in every speech not long ago.Foreign policy issues are dealt with in another joke in which Carters foreign policy is labeled "the supri-i-se foreign policy."

Even Kennedy's touchstone issue at the moment -- his calls for immediate wage-price controls -- is often tossed off in a single sentence in his stump speeches. The candidate discussed the point more completely in media interviews, however.

The Kennedy camp is uncertain what effect the new campaign style will have, but there was one sign of confidence this weekend.

The Kennedy camp summoned their new advertising man, David Sawyer, to Philadelphia Monday to film commercials for use in later primary states.

Meanwhile, Vice-President Mondale was beginning a final campaign push for the president in Pennsylvania with appearances today in Erie and tonight in Pittsburgh.

While Kennedy has been ridiculing the administration's largesse to cities in key primary states, Mondale pointed to specific benefits he said federal grants have meant to aging cities such as Erie.

"We have done more for the cities than any administration in history," he said.

The vice president also jabbed mildly at Kennedy, asserting that on major issues such as inflation the Massachusetts senator has provided no real answers.

"On the tough issues he runs away from it," Mondale said.