In this Nov. 6, 2006, file photo, President George W. Bush jokes with his brother Florida Gov. Jeb Bush in Pensacola, Fla., where the president was drumming up support for local Republican candidates. Jeb Bush is summoning his brother, former President George W. Bush, to campaign for him in South Carolina. It聮s not without risks, but the Bush family has long, deep political ties in the state, and the former Florida governor has little choice if he wants to join his father and brother as Oval Office occupants. AP File Photo
CHARLESTON, United States鈥擣ormer US president George W. Bush was launching into the caustic Republican nomination fray Monday in support of his candidate brother Jeb, whose rival Donald Trump unleashed a new round of invective at his challengers.
The political rhetoric in the presidential race has sharpened dramatically since the Iowa caucuses and the New Hampshire primaries earlier this month ahead of next Saturday鈥檚 crucial South Carolina primary.
READ: Seeking applause line, Jeb Bush struggles with voters
The mini brawls were on the verge of spilling into open warfare ahead of the February 20 vote, the third statewide contest in the long battle for the Democratic and Republican nominations to run for president.
Jeb Bush, the onetime favorite seeking to build momentum in a state where his dynastic family remains popular, was preparing to campaign later Monday鈥擯resident鈥檚 Day in the United聽States鈥攚ith his brother, who was making his first appearance stumping for Jeb.
READ: Flagging in polls, Jeb Bush drafts mom into campaign
Trump rounded on the former president during Saturday鈥檚 debate in a bid to blunt any Bush progress, and he continued the assault Monday at a press conference, slamming George W, who was president during the 9/11, 2001 terror attack on the World Trade Center.
鈥淪o you had that. You obviously had the war which was a big mistake. I think few people would say the war in Iraq was a positive,鈥� Trump said.
Trump also scolded Senator Ted Cruz, his current closest competitor, as 鈥渢otally unstable鈥� and a 鈥渓iar鈥� for attacking Trump鈥檚 earlier, liberal positions on abortion and health care.
And he repeated his threat to sue Cruz over his eligibility to be president, with Trump insisting that Cruz, who was born in Canada, is not a natural born citizen as the US Constitution requires candidates to be.
Republican 鈥榙isgrace鈥�
At an event in Mount Pleasant, the brash billionaire also lashed out at the party itself, calling the Republican National Committee a 鈥渄isgrace鈥� after he was loudly booed at Saturday鈥檚 Republican debate by an audience that Trump said was stacked with establishment lobbyists.
鈥淭he whole room was made up of special interests and donors, which is a disgrace from the RNC,鈥� Trump said. 鈥淭he RNC better get its act together.鈥�
Trump leads by a stunning 20 points over Cruz in the Palmetto State, known for its brutal political atmosphere.
Senator Marco Rubio, who is seeking a resurrection after fizzling in New Hampshire and finishing fifth there, is third at 14.3 percent, followed by a 10.5-percent showing for Ohio Governor John Kasich, whose impressive second place New Hampshire finish was helping him surge here.
Bush is fifth at 10 percent, with former neurosurgeon Ben Carson pulling up the rear in South Carolina with 4.5 percent.
Adding to the campaign intensity, and perhaps tearing at the very fabric of the Republican Party, candidates were digesting the implications of the political thunderclap brought by the sudden death of conservative Supreme Court justice Antonio Scalia.
His death Saturday has set off an epic election-year battle over his successor that will shape American life far into the future.
Meanwhile, Kasich has positioned himself as the man above the fray, presenting a heartening, optimistic message to voters and urging them not get sucked into the Republican-on-Republican vitriol that he says only increases the chances of a Clinton victory in November.
Democrat Hillary Clinton and her surprisingly strong challenger Bernie Sanders were converging on Nevada, which holds its vote Saturday, before they too shift to South Carolina for their own southern slugfest.