Washington (AFP) - The historic indictment of Donald Trump is a seismic moment for the 2024 US presidential campaign, but it is impossible to predict whether the political earthquake will cause lasting damage or settle in his favor.

On Thursday a New York grand jury voted to indict the twice-impeached Republican leader, who is running again for president, over a $130,000 hush money scheme to silence a porn star claiming a tryst with him in 2006.

Washington-watchers were laser-focused on the effect on Trump’s third bid for the White House – as Republicans united in denouncing his indictment as a politically motivated attempt to derail his campaign.

But Trump supporters and critics alike have voiced doubts over the legal merits of the case, which turns on whether the payment to Stormy Daniels just before the 2016 election counted as an illicit contribution to his campaign.

Detractors worry that if Trump were cleared – the Democrat John Edwards defeated a similar prosecution in 2012 – it could make it easier to cast any future indictment as a “witch hunt.”

And the charges will also likely juice turnout among Trump’s base, say analysts, catapulting him to victory in the nomination race, known as the presidential primary.

- ‘In-kind gift’ -

Florida Governor Ron DeSantis, seen as Trump’s main potential rival for the Republican nomination, denounced the indictment as “un-American” and a “weaponization of the legal system.”

DeSantis has also been careful in recent weeks to repeat the case’s most salacious details, joking that he didn’t “know what goes into paying hush money to a porn star.”

But don’t expect a stampede of Republicans to follow suit in needling Trump.

Nicholas Creel, a political analyst at Georgia College and State University, said Trump’s base in the “Grand Old Party” (GOP) was “simply too bought-in” to abandon him.

“Even now, we see Trump’s Republican competitors, such as former vice president Pence, actively defending him in this scandal instead of using it to attack him for his own gain,” he told AFP.

“This indicates that Trump’s GOP rivals fully understand how his base has an unshakable cult-like devotion to him, one that isn’t letting up any time soon.”

That fealty has been exemplified by the Republican majority in the House of Representatives.

Kevin McCarthy, the top Republican in the House and second in line to the presidency, lashed out at Manhattan District Attorney Alvin Bragg, a Democrat, who pushed the criminal inquiry against Trump.

Bragg “weaponized our sacred system of justice against President Donald Trump,” McCarthy said.

A trio of House committee chairmen has called on Bragg to testify before lawmakers – a stunning intervention in an ongoing case – accusing him of pursuing “sham” charges because Trump is running for president.

In the Senate, Trump loyalist Ted Cruz, a former presidential rival, said on his podcast the prosecution “could be the single biggest in-kind gift to the Donald Trump campaign of this entire cycle.”

- ‘Undying support’ -

On the left, figures like former White House strategist David Axelrod have characterized the hush money scandal as the least significant of four criminal probes of Trump.

Nerves are said to be jangling in Trumpworld over potential racketeering and conspiracy charges in a much more consequential probe of the 76-year-old billionaire’s efforts to overturn Georgia’s 2020 election results.

And a quasi-independent federal prosecutor is overseeing historic investigations into Trump’s mishandling of classified documents and involvement in the 2021 insurrection by his supporters at the US Capitol.

“Trump getting indicted should absolutely ruin his presidential aspirations. It should. But based on the undying support from his base, I do not believe it will,” Amani Wells-Onyioha, a Democratic election strategist, told AFP.

“In fact, I think it will give him a surge in the polls and cause his base to rally around him even more.”

That said, the tide of Republican opinion is showing some signs of turning, even in the House, faced with Trump’s mushrooming scandals.

Chip Roy, a right-wing lawmaker who has endorsed DeSantis for president, called into the conservative commentator Glenn Beck’s radio show last week to discuss what was then a possible Trump indictment.

“Look, at the end of the day, you cannot walk away from the fact that the former president clearly paid a porn star off to hush up right before an election,” the Republican said.

“Correct,” the host replied.