Credit Doug Mills/The New York Times
DES MOINES â The presidential race hurtled over the weekend toward a watershed moment: voting that will start to reveal the true depth of Americansâ desire to cast aside traditional politicians and 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 (Donald J. 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 â advantages that usually turn candidates like Hillary Clinton and Jeb Bush, the former governor of Florida, into inevitable nominees â will be tested against the potent messages of rivals promising upheaval.
Credit Damon Winter/The New York Times
The importance of aggressive fund-raising and campaign commercials, which have cost a combined total of more than $ 100 million so far, will become suspect if the social-media-driven organizing by grass-roots groups helps yield upset victories for candidates like Mr. Sanders.
And the national mood about entrenched power â Wall Street, political dynasties and Washington â will almost certainly be reflected in the outcomes of the nominating contests this winter.
On the Republican side, Mr. Trump, who spent Saturday barnstorming across eastern Iowa, projected the supreme confidence that has defined his campaign. A Des Moines Register/Bloomberg Politics poll released Saturday found that 28 percent of likely Republican caucusgoers supported Mr. Trump, while 23 percent favored Mr. Cruz and 15 percent backed Senator Marco Rubio of Florida.
Mr. Trump, in an interview on Friday, barely dwelled on those two rivals, saying that he was already looking ahead to the prospect of a general election matchup against Mrs. Clinton, a former secretary of state and senator.
âOur popularity is strong enough to put states in play in November that Republicans donât usually win anymore: Michigan, Pennsylvania, Virginia, Florida, Ohio,â Mr. Trump said. âIâm a little surprised that Iâve done this well, to tell you the truth. But my message is something that people want to hear, more than just going along with the usual politicians.â
On Friday, he joined other Republicans in pouncing on news that Mrs. Clintonâs private computer server had handled messages later deemed âtop secret,â saying in a Trumpian post on Twitter: âThe new email release is a disaster for Hillary Clinton.â
A look at the latest results for Iowa and New Hampshire, and how this year compares to previous election seasons.
Mr. Cruz is trumpeting an anti-establishment message like Mr. Trumpâs, 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 â particularly a second-place finish â could finally show the extent of his appeal, veteran Republicans said.
âThe Iowa caucuses are all about beating expectations,â said Gov. 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 percent of likely Democratic caucusgoers backed Mrs. Clinton and 42 percent favored Mr. Sanders.
Each side deployed hundreds of volunteers on Saturday to call voters, knock on doors and test their get-out-the-vote operations for Monday night. The Clinton campaign has a larger field operation that has been trained more thoroughly than the Sanders team, the campaigns agree.
Clinton aides also spent Saturday delivering pep talks to some of their caucus precinct captains and key workers in Iowaâs 99 counties, confident that Democrats would be drawn to Mrs. Clintonâs plans to build on President Obamaâs agenda and to look for ways to forge consensus with Republicans in Washington.
âSome people want the country to change dramatically, but a lot of other people want someone who understands the country, understands the competing interests, and will find the elusive third way like Hillary will,â said Agriculture Secretary Tom Vilsack, a former Iowa governor and a key Clinton supporter here.
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The Iowa Push
The Iowa Push
CreditMax Whittaker for The New York Times
Mr. Sanders is counting on the fervor 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. But Mr. Sandersâs reputation as an anti-politician has been bruised recently, with reports of fliers in Iowa including logos from groups that had not authorized their use; one of those groups was the League of Conservation Voters, whose political arm has endorsed Mrs. Clinton.
But as Mr. Sanders campaigned on Friday in Washington, Iowa, he stuck firmly to his outsider message. âI like this Washington more than the other Washington,â he said. âMore friendly people.â
For political leaders and strategists in both parties, the start of voting holds unusual fascination this winter because several political patterns and customs are on the line. Some Democrats say the 2016 campaign could mark the âdeath of inevitabilityâ 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.
âIn the Democratic race and also the Republican one, what was once marginal â a far-left Sanders candidacy, a celebrity Trump candidacy â has now become mainstream,â said former Gov. Bill Richardson of New Mexico, a Democrat who ran for president in 2008. âWe have to take better care of our progressive wing, particularly our younger voters, or we will become a minority party. Iâm not saying move left on everything, but the big issues should be wages and economic growth.â
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.
âUniversal dismissal of Trump and Sanders. Consensus that a Bush-Clinton face-off was pretty much inevitable. Underestimation of Cruz,â Robert Shrum, a veteran Democratic strategist, said, naming a few. âClinton remains the clear favorite, but there is a liberal impulse in the party that has made her path clearly more complicated.â
Doris Kearns Goodwin, a presidential historian, said the coming caucuses and primaries would show whether Mr. Trumpâs fame and style of campaigning â through Twitter and television appearances, large rallies, and provocative and at times offensive language â was enough to prevail against Republican âsuper PACsâ and candidates with strong donor bases.
âDonald Trump has thrown out the rules that traditionally gave advantage and a seeming sense of inevitability to presidential candidates with the biggest war chests,â she said. âThe curious thing is that while Trump may have a larger fortune than his competitors, his success owes less to his money than to his celebrity.â
Even Democrats grudgingly admit that Mr. Trump has developed a message of American exceptionalism that resonates with more voters than they expected.
âI thought he would get 25 percent of the vote in places, enough to win some primaries, but whatâs amazing is that it looks like heâll get a much higher percentage of the vote than a lot of us thought,â said Gov. Dannel P. Malloy of Connecticut, a Democrat who is backing Mrs. Clinton.
But Mr. Malloy was quick to dismiss Mr. Trumpâs belief that he could be competitive in Democratic-leaning states like his own.
âI thought he wasnât smoking anything,â Mr. Malloy joked about Mr. Trump, referring to his dislike for marijuana and other drugs.
Mr. Trump said he was not assuming victories anywhere: Iowa would make things clear soon enough, and New Hampshire, where he has a strong lead in the polls, comes soon after. But he also said that when he entered the race in June, he did not expect to reach the eve of the caucuses with a real possibility of upending national politics.
âWhen Iâm ready to make a deal, and the contracts are drawn, and Iâm walking into the conference room to sign, and people say, âYou have a lock on the deal,â I say, âNo, I never say that until itâs signed,âÂ â Mr. Trump said. âIâve tried to make my whole life about winning, but no outsider enters presidential politics thinking, âIâm going to win.âÂ â