DES MOINES • The presidential race hurtled over the weekend towards a watershed moment - voting that will start to reveal the true depth of Americans' desire to cast aside traditional politicians, Washington-style compromise and embrace disruptive outsiders appealing to their passions.
After a year of countless and often conflicting polls, more than 250,000 Iowans are expected to attend caucuses on a relatively mild Monday night and render judgment on insurgent candidates who would bar Muslims from the country (Mr Donald Trump), oppose concessions to Democrats (Senator Ted Cruz of Texas) and pursue a high-tax, big-government agenda (Senator Bernie Sanders of Vermont).
Voters are poised to bring order to the race, or reorder politics, as in no other recent election. Money, experience and endorsements - advantages that usually turn candidates like Mrs Hillary Clinton and Mr Jeb Bush, the former governor of Florida, into inevitable nominees - will be tested against rivals promising upheaval.
The importance of aggressive fund-raising and campaign commercials, which have cost a combined total of more than US$100 million (S$142 million) so far, will become suspect if the social-media-driven organising by grassroots groups helps yield upset victories for candidates like Mr Sanders.
And the national mood about entrenched power - Wall Street, political dynasties and Washington - will almost certainly be reflected in the outcomes of the nominating contests this winter.
On the Republican side, Mr Trump, who spent Saturday barn-storming across eastern Iowa, projected the supreme confidence that has defined his campaign.
A Des Moines Register/Bloomberg Politics poll released on Saturday found that 28 per cent of likely Republican caucus-goers supported him, while 23 per cent favoured Mr Cruz and 15 per cent backed Senator Marco Rubio of Florida.
Mr Cruz is trumpeting an anti-establishment message like Mr Trump's, but the caucuses will show if a sitting senator can run against the system more successfully than a celebrity businessman who has never held elective office.
Mr Rubio, a career politician who is running as a next-generation leader, hopes Iowa will prove what his supporters have long said: He is the most attractive Republican to both political insiders and outsiders. While he is running third in most polls, a strong showing - particularly a second-place finish - could finally show the extent of his appeal, veteran Republicans said.
"The Iowa caucuses are all about beating expectations," said Governor Terry E. Branstad of Iowa, a Republican who has not endorsed a candidate, but has spoken against Mr Cruz.
Among the Democrats, Mrs Clinton and Mr Sanders appeared to be locked in a close race in Iowa, with the new Register/Bloomberg Politics survey finding that 45 per cent of likely Democratic caucus-goers backed Mrs Clinton and 42 per cent favoured Mr Sanders.
Mr Sanders is counting on the fervour of his supporters to topple Mrs Clinton in Iowa, which, his advisers believe, would lead to an explosion in fund-raising to help them blanket primary states with commercials.
For political leaders and strategists in both parties, the start of voting holds unusual fascination now because several political patterns and customs are on the line.
Some Democrats say the 2016 campaign could mark the "death of inevitability" if Mrs Clinton loses the first two nominating contests, in Iowa and New Hampshire, despite beginning the race with a deep bench of donors, high approval ratings among Democrats and establishment support.
She is still ahead in national polls, but Mr Sanders is seen as empowering regular voters against the will of party apparatchiks.
Voters will also determine if new political movements can still rise to power in America. The two-party system has usually produced traditional nominees in recent decades; the counterculture movement of the 1960s, the post-Watergate era in the 1970s, the Gingrich revolution in the 1990s and the Tea Party movement of recent years did not crown truly groundbreaking standard-bearers in either party.
This year could be different, given that so many assumptions about the campaign have proved wrong so far.
"Universal dismissal of Trump and Sanders. Consensus that a Bush-Clinton face-off was pretty much inevitable. Underestimation of Cruz," said Mr Robert Shrum, a veteran Democratic strategist, naming a few. "Clinton remains the clear favourite, but there is a liberal impulse in the party that has made her path clearly more complicated."
NEW YORK TIMES