IOWA CITY – The billionaire former reality TV star Donald Trump stood on stage at a fieldhouse here last week and launched into his swaggering message: "We have this incredible country, and it's run by incompetent people who don't know what they're doing," he said to a roar from 2,000 fans.

At a high school 120 miles away in West Des Moines, former Secretary of State Hillary Clinton worked to ignite her Democratic supporters. "You could not have two more different visions of who we are as Americans," she told a crowd of cheering, sign-waving supporters. "And what the Republicans are advocating are failed policies."

For the first time in eight years, Iowa's pivotal presidential caucuses are a flat-out free-for-all with no incumbent to choose. Candidates from both parties have spent millions of dollars for an edge in the first test in an already wild election year. In both races, candidates with deep political resumes and their insurgent rivals are locked in a round-the-clock weekend frenzy before Monday's voting.

The latest polls show Trump opening up a lead over top Republican rivals, Sens. Ted Cruz of Texas and Marco Rubio of Florida. On the Democratic side, a new poll shows Clinton with a slight lead over Vermont Sen. Bernie Sanders.

Iowa can make or break political campaigns. Finishing strong allows candidates to build political and fundraising momentum as the focus shifts to New Hampshire, South Carolina and then Super Tuesday, a crucial day of caucuses and primaries in 15 states, including Minnesota.

For weeks here, the campaigns have pounded Iowans with mailings, e-mail messages, television ads, and newspaper ads all pleading for their support. They have even tried to curry favor with local football players and college wrestlers. They have endured cheers, been shouted down by hecklers and in one feverish moment during a rally, a man threw tomatoes at Trump.

If there are any undecided voters left, Ray Russell doesn't know who they are.

"I think everybody by this point ought to know" who they are supporting, said Russell, an Ankeny union retiree backing Clinton.

Coach buses emblazoned with images of candidates' faces, trailed by throngs of journalists, fans and sometimes tormentors, are rumbling through every corner of Iowa, hitting pizza joints and diners, school gymnasiums and senior homes.

At a packed union hall in Des Moines last week, Sanders laid out his plan in a barking Brooklyn accent: "What a Sanders administration is about is a very radical idea — are you ready for a radical idea? — we're gonna create an economy that works for working families, not just billionaires."

Sanders clung to a message that has fueled his insurgent campaign: that the American economy is rigged for the wealthy by a political system owned by the wealthy benefactors of politicians. He promised free public college, a socialized health insurance system, a higher minimum wage, paid family leave and a $100 billion infrastructure program, paid for by higher taxes on Wall Street, corporations and the wealthy.

Although Trump belittles Sanders on the stump, calling him a "communist," the two are sometimes in agreement on issues that stoke their passionate followers. Both decry trade agreements they say have been bad for American workers.

Trump has even joined Sanders in his assessment that the political system is rigged. Yet Trump was giddy when he acknowledged that his big political contributions made him part of that money-for-influence system for decades.

Crowds cheered loudest when Trump told him he is funding his own campaign and therefore owes nothing to moneyed interests. "They come to me," he said of lobbyists, "I will say, 'Forget it.' "

Trump events drew a mix of curiosity-seekers and hardened fans, some of them saying they feel alienated from the political system and two parties they say do not care about them. A recorded message before Trump appearances instructs the crowd not to touch or harm protesters, but rather to chant, "Trump! Trump! Trump!" if one begins demonstrating.

His typically meandering, extemporaneous speech in Iowa City was frequently interrupted by demonstrators shouting and blowing whistles. Trump has made opponents furious, particularly with his incendiary rhetoric about Mexicans and banning Muslims from the country, at least temporarily. Each time a protester tries to interrupt, Trump roared back: "Get the hell outta here!"

Rubio, a first-term senator elected in the Tea Party wave of 2010, sets himself up as a more serious and electable alternative to Trump, often without mentioning him. In a Des Moines banquet hall, Rubio touted his biography as the son of working-class Cuban immigrants to argue he can't be painted as the son of privilege, even as his policy proposals include big tax cuts for the wealthy. "Hillary Clinton can't lecture me about people living paycheck to paycheck. I've lived paycheck to paycheck. I grew up paycheck to paycheck," he said.

Chris Dougherty, 48, a truck driver who lives in West Des Moines and was shopping for candidates, was impressed with Rubio's story.

"You can hear it in his voice. The sincerity in his voice is real," he said. Dougherty said he had also gone to see Trump, but grimaced, "He's a showman."

Rubio's message may be resonating among GOP voters in Minnesota, where he finished best among Republicans in head-to-head matchups with Clinton, according to a recent Star Tribune Minnesota Poll. Rubio narrowly had the highest GOP support in poll, but his lead over Cruz was within the margin of error and the poll showed Republican voters were deeply split.

Iowa Republicans are taking a close look at Cruz, who is selling himself as the race's truest believer in the conservative creed and heir to Ronald Reagan.

Amid the dark wood of Lucile's Steaks and Spirits in rural Centerville, Cruz said the country is on the verge of an "abyss," comparing the current state of America to the "failed economic policies" and "feckless and naive foreign policy" of the presidency of Jimmy Carter.

But he implored listeners to have hope, intimating he is the new Reagan, an upbeat and charismatic leader who can unite the country.

Cruz is also making a strong effort to appeal to evangelical voters, and he finished his speech by evoking a scripture passage and asking for prayer: "Ask to awaken the body of Christ to pull us back from the abyss," he said solemnly.

Trump isn't Cruz's only problem in Iowa. He is under assault here for calling for a phaseout of the Renewable Fuel Standard, which is a de facto subsidy of ethanol, and, thus, corn growers. Republican Iowa Gov. Terry Branstad took the unusual step of saying he wants to see Cruz lose in Iowa in part because of his position on ethanol.

With the help of evangelical supporters, however, Cruz can rely on grass-roots activists to parry the beating he's taking on the airwaves and from Trump, who has questioned Cruz's eligibility to run because he was born in Canada. At Cruz headquarters in Urbandale, about 50 volunteers and organizers were huddled in separate cubicles Wednesday afternoon, quietly prospecting for votes on their phones.

At Sanders' nerve center on Martin Luther King Jr. Parkway in Des Moines, Bob Brooks, a retired union carpenter and precinct co-captain, said he decides on a candidate based on where they get their campaign money. "That's a good indicator of who they're gonna be workin' for," he said. Brooks said he has earned between 20 and 30 commitments in recent weeks after about 100 conversations with Iowans, the result of 1,500 phone calls.

Kelly McMahon, a 14-year teacher who is an active Clinton volunteer, said she has spent recent weekends working for the candidate who she thinks will be the best friend to teachers and students.

McMahon said recruiting voters is not easy: "It's a cold night in February, and you're sitting in a gym or church hall for hours." But the work goes on, she said: "We have this responsibility and opportunity as Iowans. And I'm not passing that up."

J. Patrick Coolican • 651-925-5042