MANCHESTER, IA— Republican and Democratic presidential hopefuls crisscrossed the Midwestern state of Iowa in a frenzied weekend prelude before voters have their first say in the 2016 presidential race which has taken an unexpected turn with the emergence of outsider candidates who have challenged the establishment in both parties.

Iowa offers only a small contingent of the delegates who will determine the nominees at each party’s national convention in July. But Monday’s caucuses will provide a test of whether the large enthusiastic crowds turning out at rallies for real estate mogul Donald Trump and Vermont Sen. Bernie Sanders will turn into actual votes. The caucuses should also help winnow out the crowded Republican field and provide momentum heading into the Feb. 9 New Hampshire primary.

In the last major preference poll before the caucuses, Trump had the support of 28 percent of likely caucus-goers, with Texas Sen. Ted Cruz at 23 percent and Florida Sen. Marco Rubio at 15 percent. The Iowa Poll, published by The Des Moines Register and Bloomberg, also found Hillary Clinton with 45 percent support to Sanders’ 42 percent. The poll of 602 likely Republican caucus-goers and 602 likely Democratic caucus-goers was taken Tuesday to Friday and has a margin of error of plus or minus 4 percentage points.

Trump, the showman of the Republican race, made a dramatic entrance Saturday to a Dubuque rally as his jet flew low over a hangar half-filled by the waiting crowd and music played from the movie “Air Force One.” There was more drama inside, as a small group of protesters interrupted him and Trump joined the crowd in chanting “USA” to drown out the discord.

Cruz directed much of his fire at Rubio, sharply challenging his rival’s conservative credentials on the airwaves. One ad said darkly of Rubio: “Tax hikes. Amnesty. The Republican Obama.”

“The desperation kicks in,” Rubio said in response to Cruz. “From my experience, when people start attacking you it’s because you’re doing something right.”

Seeking to lower expectations, Rubio senior strategist Todd Harris said the goal in Iowa is to “finish a strong third.”

Rubio is hoping to emerge as the favorite within the establishment wing of the party heading into New Hampshire, where he is trying to fend off challenges from former Florida Gov. Jeb Bush, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich.

With the Democratic contest a likely tossup, Sanders told a Manchester rally that the outcome depended on how many Iowans invest the time and energy to make it to caucus sites. The caucuses are held at schools, churches and even private homes.

“It’s virtually tied,” Sanders said. “We will win the caucus on Monday night if there is a large voter turnout. We will lose the caucus on Monday night if there is a low voter turnout.”

The Vermont senator and self-described democratic socialist said “the eyes of America, in fact much of the world” would be on Iowa, and the state could be a model for the future of American democracy.

Clinton has worked assiduously to avoid a repeat of 2008, when then-Illinois Sen. Barack Obama scored a surprise win in Iowa. She finished third in the caucuses and her days as the prohibitive favorite for the nomination faded.

She faced the prospect of escalating political heat from revelations Friday that the private email server she used when she was Obama’s first secretary of state contained top-secret messages that should have remained within proper, secured channels.

That heat was coming from Republicans; Sanders earlier declared the email flap a nonissue in his mind. but it has still raised questions among voters about Clinton’s honesty and integrity. But Sanders has raised the issue of the large speaking fees and campaign donations that Clinton has received from leading financial firms and other corporations.

Clinton emphasized the issue of gun regulations at a rally at Iowa State University in Ames, where she was joined by former Rep, Gabby Giffords, who was severely wounded in a mass shooting in Tucson, Arizona, and her husband, former astronaut Mark Kelly. The former secretary of state drew an implicit contrast between her push for stricter laws with Sanders’ mixed record on gun control measures.

“How can we continue to ignore the toll that this is taking on our children and our country?” Clinton asked. “When you go to caucus Monday night please think of this.”

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Associated Press writers Ken Thomas, Scott Bauer, Steve Peoples, Lisa Lerer and Tom Beaumont in Iowa and Julie Bykowicz in Washington contributed to this report.