As Donald Trump steamrolls into Alabama for potentially the biggest US campaign rally of the year Friday, Republican rivals are flummoxed over how to contain the political brute now turning the presidential race on its head.
The billionaire real estate mogul has snatched up the lion's share of the attention, interest and support of Republican voters, using a combative tone to lash out at other candidates with a coarseness rarely seen at the top tier of American campaigns.
With less than five months before Iowa and New Hampshire cast the early votes in the party nominating process, Trump leads in polls across the board, leaving the remaining 16 Republican candidates in his dust. His anti-establishment clarion call has quickly become the loudest voice in US politics.
He has jetted into the heartland to attend the Iowa State Fair, and stalked former Florida governor Jeb Bush in New Hampshire this week, where he hit Bush's Iraq and immigration positions and ridiculed his floundering poll numbers.
Polls show Trump leading in both states, and in three crucial swing-states including Bush's home turf, Florida.
Now he is taking the Trump typhoon into the deep South, where outsized demand for tickets led organizers to upgrade Friday's venue from a theater, to a larger arena, and ultimately to a 43,000-seat football stadium in Mobile, Alabama.
Trump predicted as many as 40,000 people would show up, which would be a record for the 2016 campaign so far.
"We are going to have a wild time in Alabama tonight!" blared Trump on Twitter.
His extraordinary early success has Republican candidates, donors and party leaders mystified.
"No one has figured out how to handle Trump," Republican former New Jersey governor Thomas Kean told The Washington Post.
"Everyone underestimated him terribly from Day One. But as someone who knows him and knew his father -- the whole family -- I can assure you, that was a mistake."
Perhaps recognizing a need to counter the Trump machine, Bush has upped his rhetoric, snapping on Wednesday that Trump has "been a Democrat longer than being a Republican," and citing the magnate's earlier support for abortion rights and a single-payer health care system.
On Thursday, after Bush took a page out of Trump's playbook and used the controversial term "anchor babies" to describe children born in the United States to undocumented immigrants, he refused to back down.
"I don't regret it," Bush told reporters in New Hampshire.
Other candidates have gone after Trump head on, with little to show for it.
Senator Rand Paul berated him in an August 6 debate but it did minimal damage, and the Kentucky insurgent has slipped in the polls. He has also released an ad attacking The Donald, but that, too, has not moved the needle.
"It's like a science fiction film, where you shoot at him and he gets bigger," Newt Gingrich, the former US House speaker who ran for president in 2012 and like Trump was an early frontrunner, told Fox News this week.
"You're dealing with somebody who is totally different from anybody in modern politics."
Former New York governor George Pataki has offered some of the harshest condemnation, blasting Trump's antics as "demagoguery." But Pataki's is a voice from the back of the pack and it does not appear to be registering.
Donors investing millions of dollars in support of other candidates in the race are said to be mulling possible autumn ad runs attacking Trump.
But they, and some candidates like Senator Ted Cruz and New Jersey Governor Chris Christie, are treading carefully, hesitant to antagonize a political barbarian at the gates.