[Washington] Poll-leading showman Donald Trump faces the first test of his meteoric political career on February 1, when voting to elect a new US president begins.
In just over a week, around 120,000 Iowa Republicans will have the first word on their party's White House nominee.
They are telling pollsters Trump is their man.
During a six-month campaign, the 69-year-old tycoon has slapped aside conventional political wisdom, blustering and brawling his way to a lead over his rivals.
"Trumpism" is "a toxic mix of demagoguery and nonsense," said former Texas governor Rick Perry, before crashing out of the Republican race as one of the billionaire's first political fatalities.
Most Americans have looked on with bewilderment as Mr Trump has insulted Mexicans, Muslims and most of the Republican establishment.
But Mr Trump's mix of theatrics, populism and refusal to do politics-as-usual has proven a potent brew.
The latest national polls show he has a 16-point lead over his nearest rival, Texas Senator Ted Cruz.
Grassroots white Republicans appear intoxicated by a candidate who exudes confidence, shuns political correctness and challenges professional politicians they see as too timid, and as ideologically suspect.
He appeals, in the words of David Frum - a veteran of George W. Bush's White House - to "people who are irked when asked to press 1 for English."
Mr Trump has also enthralled ratings-chasing television executives who are delighted to broadcast his rallies live - as long as he delivers eyeballs.
According to statistics from the GDELT Project, Mr Trump receives roughly as much television coverage as all other Republican and Democratic candidates combined.
That leaves those trailing in his wake unable to gain momentum, while saving Mr Trump tens of millions of dollars on paid advertising.
The mogul's improbable political journey was summed up by respected University of Virginia political analysts Larry Sabato, Kyle Kondik and Geoffrey Skelley.
"The political world has moved from disbelieving that he would even follow through and become a candidate, to expecting him to wither on the vine as more conventional choices gained steam, to accepting his nomination as a distinct possibility, to speculating that he will go all the way and defeat Hillary Clinton in November," they wrote.
But come February 1, none of the polls, none of the punditry and none of the noise matter.
The first-in-the-nation ballot will be the first real test of whether Mr Trump can turn celebrity into a political movement.
Doubts remain about whether he has the campaign structure in place to turn fans into voters.
If he can, it would be a political earthquake in the Republican party.
For much of the last eight years, establishment Republicans and the party base have papered over vast differences with similar tough sounding rhetoric and a mutual disdain for President Barack Obama.
Mr Trump has fueled that long-muted battle for the soul of the party.
Many moderate Republicans view Mr Trump as an unmitigated disaster: alienating electorally vital minority groups and likely handing the Democrats a third term in the White House.
For months, their mantra has been "let me know when he wins some delegates." But there are increasing signs of panic.
The National Review, a torchbearer for conservative Republicans, devoted a whole issue to attacking Mr Trump, calling him "a philosophically unmoored political opportunist" who would trash ideological consensus inside the party.
In the face of a Trump victory in Iowa, cooler heads may point out that the state is a notoriously bad indicator of who will become the party nominee, never mind president.
In the last two cycles, Iowa Republicans have backed Rick Santorum and Mike Huckabee, who did not get within shouting distance of the nomination.
If Mr Trump loses, it will be a serious test for a candidate who promised "we will have so much winning if I get elected, that you may get bored with winning." So far Mr Trump has met each dip in the polls with a fresh airtime-earning controversy.
Whatever happens in Iowa, expect more controversy ahead.