“John Fetterman wants to release convicted murderers from prison,” warns the narrator, as a black-and-white photo of Pennsylvania’s lieutenant governor is shown beside pictures of convicted killers. A caption adds darkly: “Socialist John Fetterman loves free stuff … but we can’t let him free murderers.”

The campaign ad from Mehmet Oz, candidate for the US Senate in Pennsylvania, is vintage Republican strategy: casting a Democratic opponent as soft on crime. The party is zeroing in on fears over public safety ahead of November’s midterm elections in an effort to change the conversation from abortion, climate or democracy.

But Republicans’ own claim to be the party of law and order is this time undermined, critics say, by the behavior of its party leaders. Former president Donald Trump, who is under myriad criminal, civil and congressional investigations, is not alone. Many senior Republicans have rallied to his defence or displayed their own contempt for the rule of law.

“The Republican party is quickly becoming a party of anarchy and lawlessness,” said Larry Jacobs, director of the Center for the Study of Politics and Governance at the University of Minnesota. “This is supposed to be the party of conservative principles, of tradition, of respect for customs and rules that make society governable.

“The idea that the law does not apply to Republicans is something that has now become part of the mainstream of the Republican party. We see it in terms of the approach to elections. We see it in terms of the treatment of immigrants. Some of the actions with regard to abortion may approach that level. The Republican party appears to consider the law and the constitution to be optional and to have lost legitimacy.”

Over seven years Trump has refashioned the party in ways obvious and subtle. That has included a willingness to defend conduct that, from any other politician, would have been seen as beyond the pale.

After FBI agents searched his Mar-a-Lago home in Florida in August and seized classified documents, including some marked top secret, Trump could be indicted for violating the Espionage Act, obstructing a federal investigation or mishandling sensitive government records. The former president also faces a state grand jury investigation in Georgia over efforts to subvert that state’s election result in 2020.

Last month, Trump and his oldest three children were accused by New York’s top prosecutor of lying to tax collectors, lenders and insurers in a “staggering” fraud scheme that routinely misstated the value of his properties. Despite it all, Trump remains the frontrunner for the party’s presidential nomination in 2024.

His chief rival, Florida governor Ron DeSantis, may have violated federal law recently by using more than $600,000 in taxpayer money to lure about 50 Venezuelan asylum seekers on to flights to the small, upmarket island of Martha’s Vineyard in Massachusetts, and transporting them across state lines with a false reason.

Authorities in Massachusetts have requested that the justice department pursue a human trafficking investigation. A sheriff in Texas, where the flights originated, has also opened an investigation into whether DeSantis acted criminally under a Texas penal code that defines the crime of unlawful restraint.

The rot goes deep in the party.

Numerous members of the House of Representatives and Senate, as well as midterm candidates seeking to join them, have refused to condemn or have actively supported Trump’s “big lie” that the 2020 presidential election was stolen, siding with the violent mob on January 6 rather than the US Capitol police officers who resisted them.

Steve Bannon, a former White House chief strategist, faces up to two years in prison after being convicted on contempt charges for defying a congressional subpoena from the House of Representatives committee investigating the insurrection. Rudy Giuliani, an ex-lawyer to Trump, had his law licence suspended after a court in New York ruled that he made “demonstrably false and misleading statements” while seeking to overturn the results of the election.

In addition, Republicans have long been criticised for prioritising laws that protect gun owners over those that protect the victims of gun violence. And since the supreme court overturned the constitutional right to abortion, Republican-led states are accused of legal abuses: the justice department is suing Idaho over a near-total abortion ban.

Critics believe that such examples make a mockery of Republican efforts to saddle Democrats with rising homicide rates in Atlanta, New Orleans, Philadelphia and other cities.

Tara Setmayer, a senior adviser to the Lincoln Project, an anti-Trump group, said: “The rank hypocrisy of the Republican party trying to use these issues under the auspices of law and order when they continue to support a professional scofflaw in Donald Trump is laughable.

“Republicans have turned a blind eye to Trump’s behavior before, during and after his presidency, which is giving a permission structure to other Republican presidential hopefuls like Ron DeSantis to act in potentially extrajudicial ways to accomplish their agenda of fearmongering and ‘owning the libs’.”

Trivialising the rule of law extends to party cheerleaders. Last month, Tucker Carlson, a host on the conservative Fox News network, spoke at the funeral of Ralph “Sonny” Barger, the longtime president of the Hells Angels motorcycle club – deemed by the justice department to be linked to organised crime.

Brett Favre, an American football star who endorsed Trump for president in 2020, is embroiled in controversy after Mississippi spent millions of dollars in welfare money on his pet project, a university volleyball arena. The state’s then-governor, Republican Phil Bryant, texted Favre in 2019 that federal money for children and low-income adults is “tightly controlled” and “improper use could result in violation of Federal Law”.

Yet Republicans have always been quick to accuse Democrats of flouting the law. In 2015 they argued that Barack Obama’s administration acted illegally when it hid a prisoner swap that freed the army sergeant Bowe Bergdahl from the Taliban. Ilya Shapiro, a former vice-president of the Cato Institute thinktank in Washington, wrote that “the Obama administration has been the most lawless in US history”.

But Setmayer, a former Republican communications director on Capitol Hill, believes that such comparisons are disingenuous. “These are the same Republicans who ran around with their hair on fire, concerned with what President Obama was doing through executive orders on guns and on immigration. That was nowhere near as legally dubious as what Republicans are doing today.”

It was 1968 when presidential candidate Richard Nixon claimed the mantle of “law and order” for the Republican party, promising to fix a nation in disarray: “As we look at America, we see cities enveloped in smoke and flame. We hear sirens in the night.” Six years later, Nixon was forced to resign after breaking the law in his efforts to cover up the Watergate break-in.

But Republicans believed they had found a winning message. In 1988, a political action committee supporting George HW Bush’s election campaign funded an ad blaming Democratic rival Michael Dukakis for the case of Willie Horton, an African American convict who committed rape during a furlough from prison. Bush’s campaign manager, Lee Atwater, boasted that he would make Horton “Dukakis’s running mate”.

Now, the familiar drumbeat is being heard again in midterm races from Oregon to Pennsylvania, from New Mexico to Washington state. House Republicans just launched a “Commitment to America” manifesto that blamed “defund the police” efforts for law enforcement officers’ tough working conditions, “to say nothing of the liberal prosecutors and district attorneys who fail to do their job and keep criminals off the streets”.

Joe Biden and other Democrats have worked hard to disown the “defund the police” slogan, with many Democratic-led cities pouring money into police departments. But the issue remains a vulnerability: voters say they agree more with Republicans on crime and policing by a margin of 10 percentage points, a recent New York Times/ Siena College poll found.

Donna Brazile, a former interim chair of the Democratic National Committee, said: “The Republicans are basically using the same playbook that Richard Nixon used. Richard Nixon ran as the candidate of law and order and we all know what happened next: Watergate. This is the same playbook. The Republicans constantly go back to their old playbooks in order to find a new way to reach the electorate. I think voters are smarter.”