Donald Trump tried to reset his campaign at a rally in battleground Pennsylvania on Saturday as polls show Kamala Harris pulling ahead in key swing states.

But the former president quickly broke away from the prepared speech about economic issues to launch personal attacks on Harris including accusations that her agenda is both communist and fascist, and that she has “the laugh of a crazy person”.

Trump’s written speech before a mostly filled 8,000-seat indoor arena in Wilkes-Barre focussed on economic policy. Some Republican strategists had hoped the former president could regain the initiative by zeroing in on issues on which opinion polls say voters have greater trust in Trump than the Democrats, such as inflation.

Trump attacked Harris as part of the Biden administration for the surge in prices that has hit many Americans hard and described increased household costs as “the Kamala Harris inflation tax”.

“She was there for everything,” he said in attempting to pin Biden’s policies on her.

Trump also likened Harris’s pledge on Friday to tackle high grocery costs by targeting profiteering by food corporations, and to bring down housing and prescription drug costs, to the Soviet Union’s economic system.

“In her speech yesterday, Kamala went full communist,” he said. “Comrade Kamala announced that she wants to institute socialist price controls. You saw that never worked before … It will cause rationing, hunger and skyrocketing prices.”

The former president challenged voters to ask themselves whether they were “better off with Kamala and Biden than you were under President Donald J Trump”, a question that many in Pennsylvania might answer in his favour.

But the impact was soon lost as Trump once again veered repeatedly away from the script with rambling discourses from immigration to China and trans people, often based on outright falsehoods.

At one point, he even acknowledged that was what he was doing.

“They’ll say he was rambling. I don’t ramble. I’m a really smart guy, you know, really smart. I don’t ramble. But the other day, anytime I hit too hard, they say he was rambling, rambling,” he said.

The audience, some wearing T-shirts proclaiming “I’m voting for a convicted felon” and chanting “Fight, fight, fight” in reference to the former president’s words shortly after he narrowly escaped an assassination attempt last month, urged Trump on.

When he returned to the script, Trump attacked Harris for her previous opposition to fracking, an unpopular stance in Pennsylvania, which is a major fracker, but he will not have helped himself in the Rust belt by saying he would cut spending on infrastructure such as renewing bridges and roads, which has provided jobs in the region.

Trump also challenged Harris’s legitimacy as the Democratic presidential candidate, describing it as “a coup” against Biden.

“Joe Biden hates her. This was an overthrow of a president,” he said.

Trump confused some in the audience with what appeared to be a claim that if Harris could become the candidate without a primary election, then so should he because he is so popular among Republicans.

“I said, so why are we having an election? They didn’t have an election. Why are we having an election?” he said.

Trump described Harris’s decision to pass over Pennsylvania’s governor, Josh Shapiro, as her running mate, as antisemitism in an apparent reference to debate about whether Shapiro’s support for Israel, including work for the Israel embassy in the past, would damage the Democratic campaign because of the war in Gaza .

“They turned him down because he’s Jewish. That’s why they turned him down. Now, we can be politically correct and not say that. I could say, well, they turned him down for various reasons. No, no, they turned him down because he’s Jewish,” said Trump.

“And I’ll tell you this, any Jewish person that votes for her or a Democrat has to go out and have their head examined.”

Through it all, Trump repeatedly returned to personal attacks on Harris, including a bizarre discourse on how she laughs, a mannerism that has proven popular among many younger voters in particular.

“Have you heard her laugh? That is the laugh of a crazy person. That is the laugh of a crazy, the laugh of a lunatic,” he said.