Republicans in Congress who are relying on Donald Trump to excite voters in the fall elections are not only defending the former president against the FBI search of his Mar-a-Lago home but politically capitalising on it with grave and potentially dangerous rhetoric against the nation's justice system.

The party that once stood staunchly for law-and-order has dramatically reversed course, stirring up opposition to the FBI and tapping into political grievances and far-right conspiracies that fed the deadly January 6, 2021, attack on the US Capitol.

It's all part of the GOP's election year strategy to harness voter outrage over the unprecedented search, quickly and unequivocally set in motion as Trump hosted a dozen Republicans for dinner of steak and scallops at his private Bedminster club the day after the FBI action.

One Republican at the table, Rep. Troy Nehls of Texas, a former sheriff, said he told the former president “loud and clear” that it's time to protect himself politically by declaring his 2024 campaign for the presidency.

"Mr. President, I said, the American people, your supporters, are concerned with this corrupt DOJ and the FBI."

“If I were you, sir, announce you're running for president," Nehls recalled telling Trump. "Take that doubt, take that anxiety away from the people that want you to be our 47th president.”

The escalating rhetoric comes amid stark warnings of violence against law enforcement, including the Ohio police shooting on Thursday of an armed man clad in body armour who tried to breach the FBI's Cincinnati office and engaged in an hours-long standoff.

The day before, FBI Director Christopher Wray had called the threats to agents and DOJ “deplorable”.