WASHINGTON (AP) — 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."

Exactly four weeks before Election Day and with his campaign floundering, 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 House Speaker Paul 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!"

Rage against fellow Republicans from the face of the 2016 GOP exposed a party slipping from mere feuding into verbal warfare with advance voting already underway in roughly half the states. Polls suggest Trump is headed toward a loss of historic proportions if he doesn't turn things around.

His scorched-earth approach, days after his sexual predatory language caught on tape triggered a mass Republican defection, threatened to alienate even more supporters.

"Fighting for the sake of fighting is not really very helpful," said former Trump adviser Barry Bennett.

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.

At the same time, Trump's campaign is considering whether to feature Bill Clinton accusers at his upcoming rallies. Trump shocked the political world before Sunday's debate by appearing with several women who had accused the former president of sexual impropriety decades earlier.

The aggressive shift is in line with the philosophy of recently hired campaign official

Steve Bannon, whose conservative website has long fueled attacks on Republican leaders and perpetuated popular conservative conspiracy theories. Bannon is now leading the campaign's messaging.

The approach has done little to endear Trump to anxious party leaders. At least 40 Republican senators and congressmen have revoked their support for the embattled Republican nominee — with nearly 30 of them urging him to quit the race altogether.

Republican Speaker Ryan, in a Monday conference call with congressional Republicans, said he would no longer campaign with Trump. He said he would focus instead on ensuring Clinton doesn't get a "blank check" with a Democratic-controlled Congress, all but conceding that Trump would lose the presidential contest.

Yet Trump's aggressive shift is popular among his most loyal supporters who continue to flock to his rallies by the thousands.

"He's fighting for us," said Megan Johnston, 54, who was among an estimated 2,000 people who packed into a high school gym to see him on Monday near Pittsburgh. She shrugged off his sexually aggressive comments in the 2005 video and pointed at Democrat Hillary Clinton's shortcomings.

"He said what he said and he apologized. She should be in jail," Johnston said.

While Trump devoted much of his fire to fellow Republicans on Tuesday, he did not ignore his Democratic opponent.

His campaign released a new ad that focuses on Clinton's recent bout with pneumonia. The ad features images of masked gunmen and nuclear weapons as a sick Clinton stumbles toward a vehicle.

"Hillary Clinton doesn't have the fortitude, strength or stamina to lead in our world," the narrator declares.

Meanwhile, Trump's campaign and the Republican National Committee declared that hacked emails released by WikiLeaks on Tuesday showed collusion between the Clinton campaign and the Department of Justice during an investigation into the former secretary of state's email server.

The evidence does indicate there was communication between the two about a court hearing date. But such dates are not inside information. They would have been publicly posted in advance on the court's docket.

The emails show that in May 2015, Clinton spokesman Brian Fallon alerted other staffers that the Justice Department was proposing to publish Clinton's work-related emails by January in response to requests by news organizations. Fallon, a former Justice Department spokesman, wrote that unspecified "DOJ folks" told him there was a court hearing planned soon in the case.

The name and email address of the person who shared the information with Fallon had been deleted.

As some Republicans fought to focus Trump's anger on Democrats, another longtime Trump ally openly considered walking away.

New Jersey Gov. Chris Christie said he was still grappling with Trump's comments from the video, calling them "indefensible." He said he still supported Trump "at this point" but was thinking about that.