Speaking in Pennsylvania on Saturday, at his first rally since the FBI searched Mar-a-Lago for top-secret material taken from the White House and since Joe Biden used a primetime address to warn that Republicans were assaulting US democracy, Donald Trump lashed out.

The former president said: “The FBI and the justice department have become vicious monsters, controlled by radical-left scoundrels, lawyers and the media, who tell them what to do.”

Trump nominated the FBI director, Christopher Wray, in 2017.

Biden spoke outside Independence Hall in Philadelphia, a site with tremendous resonance in US history, on Thursday night.

Presenting a “battle for the soul of the nation”, he said: “This is a nation that rejects violence as a political tool. We are still, at our core, a democracy. Yet history tells us that blind loyalty to a single leader and the willingness to engage in political violence is fatal in a democracy.”

In Wilkes-Barre on Saturday night, Trump called Biden’s remarks “the most vicious, hateful, and divisive speech ever delivered by an American president”.

The former president was appearing in support of Mehmet Oz, the Republican candidate for US Senate, and Doug Mastriano, the candidate for governor.

Oz, a TV doctor, is struggling against the lieutenant governor, John Fetterman. On Saturday night, Trump called the Democrat “a socialist loser”. He also claimed without evidence that Fetterman, who recently suffered a stroke and whose health has been mocked by the Oz campaign, used illegal drugs.

“Fetterman supports taxpayer-funded drug dens and the complete decriminalization of illegal drugs, including heroin, cocaine, crystal meth, and ultra lethal fentanyl,” Trump said. “By the way, he takes them himself.”

Trump also said: “Fetterman may dress like a teenager getting high in his parents’ basement, but he’s a raging lunatic hell-bent on springing hardened criminals out of jail in the middle of the worst crime wave in Pennsylvania history.”

Mastriano is a supporter of Trump’s lie that Biden’s 2020 election victory was the result of electoral fraud. The candidate has compared the January 6 assault on the US Capitol to the Reichstag fire, the event in Berlin in 1933 which propelled Adolf Hitler to power. He has also been photographed wearing the uniform of a Confederate soldier.

Biden’s speech continues to resonate. In Philadelphia, he spoke against a dramatic, deep-red background. Republicans protested, some saying the speech was too political to be delivered amid the trappings of the presidency, including attendant US Marines.

On Sunday, Tiffany Smiley, the Republican candidate for Senate in Washington state, was asked on CNN’s State of the Union if she believed Biden won the 2020 election fairly and legitimately – a question now asked of most Republican candidates for state and national office.

Smiley said she did. But she also said she was “extremely disappointed” with the speech in Philadelphia, “because unity is not conformity. And I think President Biden got that really, really mixed up”.

Michael McCaul, a Republican congressman from Texas, told ABC’s This Week: “If this was a speech to unify the American people, it had just the opposite effect. It basically condemned all Republicans who supported Donald Trump in the last election. That’s over 70 million people.”

More than 81 million voted for Biden. In his speech, the president said he wanted “to be very clear, very clear up front: not every Republican, not even a majority of Republicans, are Maga [pro-Trump] Republicans … [who] represent an extremism that threatens the very foundations of our republic.”

In Wilkes-Barre, Trump told his audience that under Biden, they were “enemies of the state”. Of Biden, he said: “He’s an enemy of the state, you want to know the truth.”

Of the FBI search at Mar-a-Lago, Trump said: “It was not just my home that was raided last month. It was the hopes and dreams of every citizen who I’ve been fighting for.”

Calling the search “one of the most shocking abuses of power by any administration in American history” and “a travesty of justice”, he said: “They’re trying to silence me and more importantly they’re trying to silence you. But we will not be silenced, right?”

Investigators recovered thousands of documents, including more than 100 with classified and top-secret markings. A Trump-appointed judge is considering Trump’s request for the appointment of a court official to review the documents for any covered by executive privilege.

Trump won Pennsylvania in 2016, one success in a string of usually Democratic states which fueled his victory over Hillary Clinton. But Biden won it in 2020, its call four days after election day putting him in the White House. As the 2022 midterms approach, Biden is due back in the state on Monday, the Labor Day holiday, for an event in Pittsburgh.

Reporters in Pennsylvania for Trump’s rally found support for the former president over the Mar-a-Lago search. Roy Bunger, 65, told the New York Times the Biden administration was “deliberately targeting” Trump “to keep him from running again”.

But there are signs that Trump’s endorsement will not be enough to help Oz win a Senate seat Republicans have targeted in their attempt to take back the chamber. Larry Mitko voted for Donald Trump in 2016. He told the Associated Press he would not back Oz, “No way, no how.”

Mitko said he did no feel like he knew the celebrity heart surgeon, who narrowly won his May primary with Trump’s backing. Mitko said he would vote for Fetterman, with whom he has been familiar with since Fetterman was mayor of nearby Braddock.

“Dr Oz hasn’t showed me one thing to get me to vote for him,” he said. “I won’t vote for someone I don’t know.”