WASHINGTON — The “shackles” gone, Donald Trump stepped up his fierce attacks on his own party leaders, promising to teach Republicans who oppose him a lesson and to fight for the presidency “the way I want to.”

“I’m just tired of non-support” from leaders of the party he represents on the presidential ticket, Trump said Tuesday evening on Fox News Channel’s “The O’Reilly Factor.” He saved special ire for House Speaker Paul Ryan, who told Republicans Monday he’ll no longer campaign for Trump with four weeks to go before Election Day.

“I don’t want his support, I don’t care about his support,” Trump said. “I wouldn’t want to be in a foxhole with a lot of these people, that I can tell you, including Ryan. By the way, including Ryan, especially Ryan.”

With his campaign floundering and little time to steady it, the businessman reverted to the combative, divisive strategy that propelled him to victory in the GOP primary: Attack every critic — including fellow Republicans. Those close to Trump suggested it was “open season” on every detractor, regardless of party.

“It is so nice that the shackles have been taken off me and I can now fight for America the way I want to,” Trump said in a tweet that brought new concern — near panic in some cases — to a party trying to stave off an all-out civil war before Nov. 8.

In tweets, the Republican nominee called Ryan “weak and ineffective,” Sen. John McCain “very foul-mouthed” and “disloyal” Republicans “far more difficult than Crooked Hillary.” “They come at you from all sides,” Trump declared. “They don’t know how to win — I will teach them!”

At a night rally in Florida hours later, Trump made no mention of the apparent Republican civil war, instead training his fire on his Democratic opponent Hillary Clinton.

Trump has acknowledged the possibility of defeat in recent days, but on Tuesday he tried to shift the blame for his struggles on Republican defections and an election system that may be “rigged” against him. On Monday, he warned of potential voter fraud in heavily African-American Philadelphia, a claim for which there is no evidence but one that could challenge Americans’ faith in a fair democratic process.

Yet Trump’s aggressive shift is popular among his most loyal supporters.

Allison Ellis, 30, deemed Ryan “a traitor” and shrugged off Trump’s sexually aggressive comments in the 2005 video. She pointed at Democrat Hillary Clinton’s shortcomings.

“I have daughters and I don’t like what he said but I also wouldn’t want to be held responsible for everything I said 11 years ago,” Ellis said at Trump’s Panama City Beach, Fla., rally.

But some of Trump’s supporters admitted their confidence was shaken.

“I still think he can do it, but he has to play mistake-free the rest of the way,” said Mike Novoret, 59. “If something else comes up, he’s toast.”

As the GOP battled itself, Clinton focused on climate change in swing state Florida alongside former Vice President Al Gore. Gore, whose 2006 documentary “An Inconvenient Truth” focused on global warming, said Clinton would “make solving the climate crisis a top national priority.”

Trump’s campaign released a new ad that focuses on Clinton’s bout with pneumonia. The ad has images of masked gunmen and nuclear weapons as a sick Clinton stumbles toward a vehicle.