[WASHINGTON] Embattled presidential hopeful Donald Trump lashed out against "disloyal" Republicans in a ranting tweetstorm Tuesday, deepening a split that threatens the future of the 162-year-old party.
Declaring himself unchained from party strictures, the White House nominee berated Republican leaders for offering him "zero support" and promised a bareknuckle 28-day campaign against Hillary Clinton.
Mr Trump ridiculed the party's 2008 White House nominee John McCain as "very foul mouthed." He called Paul Ryan, the nation's top elected Republican, a "weak and ineffective leader." "It is so nice that the shackles have been taken off me and I can now fight for America the way I want to," Mr Trump said in a three-hour cyber outburst. "I will teach them!"
Relations between Mr Trump and party leaders have always been strained - from the outset many considered the bombastic reality-TV-star-turned-politico unfit to take up the mantle of Abraham Lincoln and Ronald Reagan.
But the snapping point has been Mr Trump's precipitous fall in the polls after the emergence of a video in which he bragged about groping women.
The White House on Tuesday condemned Mr Trump's on-mic boast as "repugnant," with spokesman Josh Earnest saying most people would consider the actions described as "sexual assault."
Mr Trump has apologised for the comments, saying they were just "locker-room" banter.
The latest Real Clear Politics polling average has Mrs Clinton ahead by six points across the country, and the latest polls show her ahead in a slew of must-win states for Mr Trump.
With his campaign in a tailspin, Mr Trump seemed determined to ram a wedge between party leaders and the radicalised grassroots that propelled his political career.
For much of Barack Obama's eight years in the White House, the Republican leadership has struggled to keep hardliners inside the tent.
Now Mr Trump is fueling an intra-party war, with streams of Republicans saying they will vote for Mrs Clinton and Trump fans vowing to bring down Congressional leaders like Mr Ryan and Mr McCain.
Mr Trump's anger seems to have been prompted by Mr Ryan suggesting that fellow Republicans stop defending the party nominee and focus on limiting electoral losses in Congress.
In a conference call on Monday, Mr Ryan told congressional Republicans "you all need to do what's best for you in your district," according to one person who listened in.
But Mr Trump's belligerent reaction is an ominous sign for Republicans worried about losing control of the House of Representatives and the Senate.
"Disloyal R's are far more difficult than Crooked Hillary. They come at you from all sides. They don't know how to win - I will teach them!" Mr Trump tweeted.
Mr Trump's campaign has long had a no holds barred quality but the break with Republicans signals the start of an even more vitriolic campaign.
Mr Trump has also alienated allies by bringing up unproven sexual abuse allegations against Clinton's husband, former president Bill Clinton, in a debate Sunday watched by tens of millions of Americans.
The last few days have seen Hillary Clinton's speeches interrupted by people shouting "Bill Clinton is a rapist!" A right-wing website has offered US$5,000 to anyone who goes to a rally and does the same.
An unsparing Trump campaign ad released on Monday showed Hillary Clinton when she had pneumonia last month, coughing at a dais and stumbling as she tried to get into her motorcade after a 9/11 anniversary ceremony.
"Hillary Clinton doesn't have the fortitude, strength or stamina to lead in our world," the narrator says.
Also Monday, Mr Trump suggested to a mostly white audience in Philadelphia, which has a large African-American population, that the election may be "stolen" by "other communities."
Mrs Clinton's campaign will be eager to tether the whole Republican Party to Mr Trump's harsh message - which is popular with the party base but appears to have little appeal with the wider public.
"Somewhat of a civil war is breaking out in the Republican Party," said Clinton communications director Jen Palmieri. "But I think that Donald Trump didn't become the nominee of his party on his own."
She accused elected Republicans of helping to "legitimise him," adding, "I think they have a lot to answer for and the voters I imagine will hold them accountable (in) House and Senate races."
Mrs Clinton revived the Clinton-Gore 1992 White House ticket on Tuesday, campaigning in Miami with her husband's vice-president Al Gore.
Mr Gore has been largely absent from politics since he lost the 2000 race in Florida to George W. Bush by a handful of votes.
In Miami he focused on the high stakes of November's election. "Your vote really, really, really counts. You can consider me as Exhibit A."
Mrs Clinton will have another potent surrogate on the campaign trail on Tuesday when President Barack Obama travels to Greensboro, North Carolina.