Donald Trump is conjuring his most foreboding vision yet of a possible second term, telling supporters in language resonant of the run-up to the January 6 mob attack on the US Capitol that they need to "fight like hell" or they will lose their country.

The rhetorical escalation from the four-times-indicted ex-president came at a rally in South Dakota on Friday night where he accused his possible 2024 opponent, President Joe Biden, of ordering his indictment on 91 charges across four criminal cases as a form of election interference.

"I don't think there's ever been a darkness around our nation like there is now," Trump said, in a dystopian speech in which he accused Democrats of allowing an "invasion" of migrants over the southern border and of trying to restart Covid "hysteria."

The Republican front-runner's stark speech raised the prospect of a second presidency that would be even more extreme and challenging to the rule of law than his first. His view that the Oval Office confers unfettered powers suggests Trump would indulge in similar conduct as that for which he is awaiting trial, including intimidating local officials in an alleged bid to overturn his 2020 defeat.

Characteristically, Trump also turned criticism of his behavior against his political foes, implicitly arguing that the true peril for America's political freedoms did not spring from his attempt to invalidate a free and fair election, but from efforts to make him face legal accountability for doing so. "It's really a threat to democracy while they trample our rights and liberties every single day of the year," he said.

"This is a big moment in our country because we're either going to go one way or the other, and if we go the other, we're not going to have a country left," he told supporters in South Dakota. "We will fight together, we will win together and then we will seek justice together," he added. This followed a March rally in which he billed his 2024 campaign and potential second term as a vessel of "retribution" for supporters who believe they've been wronged.

Trump is a highly skilled demagogue whose facility for injecting falsehoods and conspiracies into the country's political bloodstream creates a swirl of chaos and acrimony in which he alone seems to prosper. And his words shape public opinion. In a recent CNN poll, for example, only 28% of Republicans thought Biden legitimately won sufficient votes to win the 2020 election. This comes after years of Trump incessantly denying he lost, and despite courts throwing out his multiple challenges to the result.

Trump's authoritarianism may make the 2024 election a profound choice

The autocratic cast of Trump's campaign is creating an ominous atmosphere around the 2024 election and generating profound dilemmas for voters and his opponents. It, for instance, lends extra importance to a growing debate over whether Biden, at the age of 80, has the necessary stamina and political resilience to beat Trump a second time. While his predecessor spent the weekend casting doubt on America's election system, Biden was on the other side of the globe in India and Vietnam building international support for his signature foreign policy strategy of combating the threat to Western democracy from authoritarian leaders in China and Russia.

Back home, the ex-president's extremism also exposes the timidity of most of his Republican primary rivals, who have recently been ganging up on rookie candidate Vivek Ramaswamy but are only willing to criticize Trump in the most oblique terms to avoid crossing his millions of GOP supporters. About the closest that one candidate, former South Carolina Gov. Nikki Haley, came to criticizing Trump's conduct on CNN's "State of the Union" on Sunday was to warn that "we need to leave the negativity of the past behind us" as she promoted herself as the exemplar of a new generation of leadership.

The former president's increasing demagoguery also puts the spotlight on key unknowns of the 2024 election:

-- Does the GOP risk nominating a candidate whose untamed behavior will alienate voters in many suburban swing districts who turned against him in the 2020 election, especially given the possibility that he could be a convicted felon by the time voters make their choice?

-- And if Trump wins the nomination, will his liabilities and the prospect of four more years of chaos and recriminations mitigate concerns about Biden's physical and mental competence and concerns about the economy, as revealed in a CNN poll last week that captured a broadly negative view of his presidency?

At the same time, Trump's strong lead in the primary shows there is a market for his brand of strongman theatrics. Millions of voters trust and admire him and have been persuaded both by his false claims that he won the 2020 election and that the criminal indictments he is facing are an attempt to persecute him for his political views. Trump's bluntness and carefully maintained image as an outsider, despite the fact that he used to live in the White House, allow him to endlessly tap a seam of resentment against Washington and political, economic and media "elites" that is deeply felt by many who back the "Make America Great Again" movement. This perhaps explains why his indictments seem to have made him more popular in the GOP primary.

And schooled by Trump, Republicans widely complain that the current president's son, Hunter Biden -- who is under investigation by a special counsel over alleged tax and gun law violations after the collapse of a plea deal -- is being given preferential treatment by the Justice Department. And they're calling out corruption in what they see as Hunter Biden's attempts to take advantage of his father's former position as vice president to close business deals in places like China and Ukraine.

Trump has sown and propagated many of these narratives for months, putting political pressure on GOP leaders on Capitol Hill to consider the possibility of an impeachment inquiry into Joe Biden. Supporters of the move have not yet shown which high crimes or misdemeanors, or instances of treason or bribery -- the constitutional standard for impeachment -- apply to Biden. The president has denied being involved in any of his son's business dealings, and Republicans haven't produced any evidence of wrongdoing on his part in relation to those deals. Still, a majority of Americans in a recent CNN survey -- 61% -- say they think that Joe Biden had at least some involvement in Hunter Biden's business dealings, with 42% saying they think he acted illegally, and 18% saying that his actions were unethical but not illegal. A 55% majority also say the president has acted inappropriately regarding the investigation into his son over potential crimes, while 44% say that he has acted appropriately.

These national splits that Trump expertly widens speak to a deep sense of alienation in American politics that will only be exacerbated by a bitter election. Such a divide was on graphic display at a football clash on Saturday in the first-in-the-nation GOP caucus state where Trump, one of several GOP candidates to attend the game, was greeted by a mix of cheers and boos. Several football fans gave him a one-fingered salute in gestures captured on social media. The host Iowa State Cyclones lost to the University of Iowa Hawkeyes at the game in Ames, a college town in Story County -- a liberal bastion in an increasingly conservative state that Trump twice carried in general elections.

Why Trump's language is the engine of his political power

Some commentators have previously questioned what they see as alarmist media coverage of Trump, suggesting his performative belligerence is often interpreted too literally. But the hundreds of pages of evidence in criminal indictments alleging Trump's use of presidential power to try to steal an election and the way he is using his appearances and social media to try to intimidate judges and potential jury pools ahead of his trials have left such critiques badly outdated.

Trump's fiery rhetoric is central to his political appeal and his method of building power. From his biting put-downs and nicknames that belittle rivals, to the speech in Washington before he told the crowd to "fight like hell" or they wouldn't have a country on January 6, 2021, Trump uses language to drive his political movement.

In his remarks in South Dakota -- where he accepted the endorsement of Gov. Kristi Noem, a potential vice presidential pick if he is the GOP nominee -- Trump complained that he was the victim of "corrupt and blatant" victimization and "election interference." He said the cases filed against him would "allow" him, if elected president, to call up his attorney general and demand an investigation into his political adversaries. "Indict my opponent, he's doing well," Trump said, implying that was exactly what Biden had done. The ex-president used a sarcastic tone in the raucous atmosphere of a campaign rally, so context is important. But given his example of following through on his threats, his comments may end up being predictive if he wins in 2024.

He frequently argued as president that he had all but unfettered constitutional power, which is an attitude that is clearly in evidence in three of his indictments -- over attempts to overthrow the election and over his hoarding of classified documents after leaving the White House.

So, when Trump issues threats on the campaign trail, it's worth listening.