SPARTANBURG, United States (AFP) - It will be hard to slow down the Trump train. Just ask retired railroad conductor Tommy Redden.

Redden and hundreds of other Trump supporters packed into a hotel ballroom in Spartanburg to celebrate his South Carolina primary win Saturday (Feb 20), expressing confidence the billionaire can roll on to the Republican presidential nomination.

"He's not a politician. He's a man that'll be more honest than Ted Cruz or Marco Rubio or Jeb Bush - or Hillary or Bernie," an ecstatic Redden, 67, told AFP as he awaited the arrival of Trump at the watch party.

"Super Tuesday's going to tell the story with Donald Trump," he said of the critical upcoming March 1 votes in about a dozen US states. "If he does great that day, I think he'll get the nomination."

A roar swelled up the moment supporters saw TV networks calling the South Carolina contest for Trump - further evidence the anti-establishment movement of the 2016 cycle was gaining momentum.

An outsider as frontrunner in the Republican race is the new normal, obliterating the conventional wisdom that a caustic real estate tycoon who insults immigrants and his fellow Republicans with equal gusto had no business being the party's standard-bearer.

The early favorite was Bush, who was relentlessly savaged by Trump.

Jeb's poor showing in South Carolina was strike three, after dismal results in Iowa and New Hampshire, and the son and brother of two presidents suspended his campaign on Saturday (Feb 20).

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"I wasn't surprised by it," Derrick Foster, who owns a landscaping company in Spartanburg, said of Bush's departure at the Trump event.

"I think he's a good person, I think he's got a lot of knowledge. I'm just not sure he was ready for the presidency." With Trump cementing his status as the likely nominee with victories in two of the first three contests, his supporters' message was clear: This movement is for real, and it's time to dispense with the notion that Trump can't win.

"Trump's on fire!" 29-year-old Dwight Kelly declared, with an unlit celebratory cigar between his teeth.

While Kelly, a health care worker, claimed sweet victory for his candidate, he insisted the supporters were not doing any boasting. "It's not an 'I told you so'" moment, he said.

Gail Barrow, 64, said she envisioned Trump going all the way. "Oh, Mr Trump. He's amazing," said Barrow, from Goose Creek, a three-hour drive away. "He's like an Energizer bunny," she said, referring to the battery advertisement character that never stopped.

Trump may indeed be unstoppable. Slamming Mexicans as "rapists" and other criminals did not derail him. Neither did upbraiding president George W. Bush, Jeb's older brother, about the 9/11 attacks of 2001.

Nor did calling Pope Francis's comments "disgraceful" when the Holy Father questioned Trump's Christianity.

"I think he's going to be the presidential nominee, and I think he can win" the general election against Hillary Clinton or Bernie Sanders, said Johnny Gibson, a paint contractor who was first in line at the Trump party - more than seven hours before the 69-year-old Trump appeared.

For Gibson, voters see Trump's presidential bid as a good-faith commitment to civil service rather than self-promotion.

"The man could be on an island laying out in the sand, spending his money, and yet he's trying to run for office and better America," he said.

Trump, in his victory speech here with his family at his side, made no mention of Bush, with whom he clashed bitterly on the trail.

But he conceded that running for the highest office in the land took a toll.

"It's tough, it's nasty, it's mean, it's vicious," Trump observed. "It's beautiful. When you win, it's beautiful."