DES MOINES, Iowa — In a high-stakes test of enthusiasm versus organization, Republican Donald Trump and Democrat Bernie Sanders hope to ride voter energy into victories in Monday’s Iowa caucuses, as Ted Cruz and Hillary Clinton bank on sophisticated get-out-the vote operations months in the making.

The caucuses kick off the 2016 presidential nominating contests, marking a new phase in a tumultuous election that has exposed Americans’ deep frustration with Washington and given rise to candidates few expected to challenge for their party’s nomination when they first entered the race.

After months of campaigning and more than $200 million spent on advertising, the race for supremacy in Iowa is close in both parties. Among Republicans, Trump appears to hold a slim edge over Cruz, a fiery senator from Texas. Clinton and Sanders entered Monday in a surprisingly tight Democratic race, reviving memories of the former secretary of state’s disappointing showing in Iowa eight years ago.

“We knocked on 125,000 doors this past weekend,” Clinton told NBC’s Today Monday morning. “Although it’s a tight race, a lot of the people who are committed to caucusing for me will be there and standing up for me and I will do the same for them in the campaign and in the presidency.”

Sanders, the Vermont senator who has been generating big, youthful crowds across the state, urged voters to help him “make history” with a win in Iowa.

In a show of financial strength, Sanders’ campaign announced Sunday it had raised $20 million in January alone. While Sanders has a large team in Iowa, his operation got off to a later start, particularly compared with Clinton, who has had staff on the ground in the state for nearly a year.

Monday’s contest will also offer the first hard evidence of whether Trump can turn the legion of fans drawn to his plainspoken populism into voters. The scope of the billionaire’s organization in Iowa is a mystery, though Trump himself has intensified his campaign schedule during the final sprint, including a pair of rallies Monday.

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 will likely be viewed as a failure to meet expectations.

Seeking to tamp down expectations, Cruz said Sunday that he’s just pleased to be in the mix for first place.

“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 said.

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 traditionally lashed back at the attacks, adopted the same reflective tone as many of his rivals, telling NBC that Cruz “has a very strong ground game.” He diminished the 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. Republican John Kasich already had decamped to New Hampshire, with New Jersey Gov. Chris Christie and former Florida Gov. Jeb Bush following behind Monday afternoon, hours before the caucuses start.

The trio of governors has had a light footprint in Iowa, banking instead on strong showings in New Hampshire’s Feb. 9 primary to jumpstart their White House bids. Yet some Republican leaders worry that if Trump or Cruz pull off a big victory in Iowa, it would be difficult to slow their momentum.