WASHINGTON — The “shackles” gone, Donald Trump stepped up his fierce attacks on his own party leaders Tuesday, promising to teach Republicans who oppose him a lesson and 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 another series of tweets, the Republican nominee called Ryan “weak and ineffective,” Sen. John McCain “very foul-mouthed” and “disloyal” Republicans “far more difficult than Crooked Hillary.”