Donald Trump called his Democratic rival 'the devil' on Monday in a high-profile escalation of his campaign rhetoric – at precisely the moment he needed to change the subject.

Facing a four-day-long scandal over his criticism of the father of a Muslim soldier who died in combat, the Republican presidential nominee shifted gears.

Sen. Bernie Sanders, Trump told an overflow crowd at a high school in Mechanicsburg, Pennsylvania, 'made a deal with the devil' when he endorsed Clinton at last week's Democratic National Convention.

'She's the devil!' he added.

SCROLL DOWN FOR VIDEO

'SHE'S THE DEVIL!': Donald Trump went all-in on Monday night as he said that when Bernie Sanders made an endorsement 'deal with the devil,' Hillary Clinton was the Satan figure

DEAL WITH HER: Trump said Bernie Sanders made a 'deal with the devil' when he agreed to endorse Hillary Clinton during last week's Democratic National Convention

Trump has hinted at the insult before, saying Friday in Colorado that 'Bernie blew it. He sold his soul to the devil. He did.'

But Trump had previously stopped short of declaring that Hillary Clinton is, in fact, the Prince – or Princess – of Darkness.

By rallying around Clinton instead of standing on principle, the billionaire said, Sanders 'made a bad deal. He should have not made a deal. He would have gone down as [having] done something really important.'

'Once he made that deal, and believe me, he has buyer's remorse.'

'If he would have just not done anything – just go home, go to sleep, relax – he would have been a hero,' he said. 'But he made a deal with the devil. She's the devil! He made a deal with the devil. It's true.'

It's not the first time Satan has figured in this year's presidential election.

NO FINGERS? Trump celebrated his day in Ohio and Pennsylvania with KFC chicken – and a knife and fork

CAPACITY CROWD: Thousands packed a high school gymnasium to hear their plainspoken political hero speak on Monday night

NOT THE FIRST: Ben Carson connected Clinton to Beelzebub last month, saying at the Republican National Convention that her mentor Saul Alinsky had dedicated his book 'Rules for Radicals' to Lucifer

Sanders' campaign manager Jeff Weaver told CNN in April that it was Clinton who 'made a deal with the devil' by accepting millions in campaign cash from Wall Street banks.

'LUCIFER IN THE FLESH': John Boehner (pictured) used that epithet to roast Sen. Ted Cruz in April

'And we know the devil wants his money in the end,' Weaver said.

Weeks later, former House Speaker John Boehner told an audience at Stanford University that Texas Sen. Ted Cruz, who was then giving Trump a strong primary fight, was 'Lucifer in the flesh' and 'a miserable son of a b**ch.'

And Dr. Ben Carson, who may run the Department of Health and Human Services in a Trump administration, tried to tie Clinton to the devil two weeks ago during his Republican National Convention speech.

The former secretary of state, Carson said, was a disciple of far-left activist Saul Alinsky – who dedicated his book 'Rules for Radicals' to 'Lucifer, the original radical who gained his own kingdom.'

Trump's Pennsylvania speech was heavy on talk of manufacturing jobs and trade, clobbering the Clintons for their 1990s era support for the North American Free Trade Agreement.

The Republican nominee has called NAFTA the 'biggest job-killer' in recent history. It's a theme he's hit on often in rust-belt states including Pennsylvania, West Virginia and Ohio.

Trump also predicted that despite her recent flip on the Trans-Pacific Partnership, Clinton will back the multi-nation trade pact if she becomes president.