DES MOINES, Iowa (AP) — Iowa kicked off voting in the 2016 presidential race Monday night, with the Republican contest shaping up as a three-way fight among Donald Trump, Ted Cruz and Marco Rubio. Democrats Hillary Clinton and Bernie Sanders were also locked in a tight battle as the caucuses began.

The indicators were based on interviews with voters who arrived early to caucus sites across the state, conducted by Edison Research for The Associated Press and the television networks.

At stake in Iowa was crucial early momentum in the presidential campaign, and for some candidates, the future of their White House hopes altogether.

Candidates faced an electorate deeply frustrated with Washington. While the economy has improved under President Barack Obama’s watch, the recovery has eluded many Americans. New terror threats at home and abroad have also ratcheted up national security concerns.

Early-arriving voters at Republican caucuses indicated they were deeply unhappy with the way the federal government is working. Four in 10 said they were angry and half said they were dissatisfied.

Six in 10 Democratic caucus-goers wanted a candidate who would continue Obama’s policies, according to the preliminary entrance polling.

In Iowa, which has for decades launched the presidential nominating contest, candidates also faced an electorate that’s whiter, more rural and more evangelical than many states. But, given its prime leadoff spot in the primary season, the state gets extra attention from presidential campaigns.

Iowa has decidedly mixed results in picking eventual nominees. The past two Republican caucus winners — former Arkansas Gov. Mike Huckabee and former Pennsylvania Sen. Rick Santorum — faded as the race stretched on. But Barack Obama’s unexpected 2008 victory was instrumental in his path to the Democratic nomination, easing the anxieties of those who worried the young black senator would struggle to win white voters.

Clinton was seeking to overcome the ghosts of her loss to Obama in 2008. Her campaign spent nearly a year building a massive get-out-the-vote operation in Iowa.

Yet she faced an unexpected challenge from Sanders, the self-declared democratic socialist from Vermont. Sanders has drawn big, youthful crowds across the state and his campaign was hoping for high turnout.

“We will struggle tonight if the voter turnout is low. That’s a fact,” Sanders told volunteers and supporters in Des Moines.

Monday’s contest will offer the first hard evidence of whether Trump can turn the legion of fans drawn to his plainspoken populism into voters. He has intensified his campaign schedule during the final sprint, including dropping by a caucus site in West Des Moines.

Cruz has modeled his campaign after past Iowa winners, visiting all of the state’s 99 counties and courting influential evangelical and conservative leaders. With the state seemingly tailor-made for his brand of uncompromising conservatism, a loss to Trump would likely be viewed as a failure to meet expectations.

Seeking to tamp down expectations, Cruz said Sunday, “If you had told me a year ago that two days out from the Iowa caucuses we would be neck and neck, effectively tied for first place in the state of Iowa, I would have been thrilled.”

Cruz has spent the closing days of the Iowa campaign focused intensely on Marco Rubio, trying to ensure the Florida senator doesn’t inch into second place. Rubio is viewed by many Republicans as a more mainstream alternative to Trump and Cruz, though he’ll need to stay competitive in Iowa in order to maintain his viability.

Rubio, who previously lashed back at criticism, adopted the same reflective tone as many of his rivals on Monday, telling NBC that Cruz “has a very strong ground game.” He dismissed attacks against him as “politics as usual.”

The campaigns were anxiously keeping an eye on the weather. A snowfall forecast to start Monday night appeared more likely to hinder the hopefuls in their rush out of Iowa than the voters.

Republicans John Kasich, Chris Christie and Jeb Bush were all spending Monday night in New Hampshire — not only to get a jump on the weather but also on their competitors in a state with voters who are expected to be friendlier to more traditional GOP candidates.

Speaking in Hopkinton, New Hampshire, Christie urged voters to back a candidate they believe “symbolizes what this country stands for.”

Turnout was expected to be strong.

While both parties caucus on the same night, they do so with different rules.

Republicans vote by private ballot. The state’s 30 Republican delegates are awarded proportionally based on the vote.

Democrats form groups at caucus sites, publicly declaring their support for a candidate. If the number in any group is less than 15 percent of the total, they can either bow out or join another viable candidate’s group.

Those final numbers are awarded proportionately, based on statewide and congressional district voting, determining Iowa’s 44 delegates to the national convention.