One candidate made an appearance with the world’s largest tractor. Another showed up with the Duggars, the nation’s most famous large family. There were two Pauls in Des Moines. Six Romneys in Davenport.

This is Iowa, the day before the circus leaves town.

On Tuesday night, this state will hold its first-in-the-nation Republican caucuses. On Monday, six presidential candidates — including the three very different men who appear to be front-runners — all began their last dashes under Iowa’s frigid sunshine.

Former Massachusetts governor Mitt Romney’s agenda included four cities, spread over 269 miles. Former senator Rick Santorum (Pa.) drove a 171-mile circuit around Iowa’s navel. And Rep. Ron Paul (Tex.), the third candidate in the lead pack, began a long trek across northeastern part of the state, making five stops over 391 miles.

Their messages followed a familiar pattern. Romney attacked President Obama.

At a stop in Marion, he accused Obama of turning the United States into “a European-style welfare state,” saying Obama’s policies would “poison the very spirit of America and keep us from being one nation under God.”

“I’ve watched a president just become the great divider, the great explainer, the great excuse giver, the great blamer,” Romney said. “I want to have an America that comes together. I’m an optimist. I believe in the future of America. I’m not a pessimist. I believe that this country can be as it’s always been, the shining city on a hill — but not by turning into Europe or anything like Europe, but by being quintessentially American.”

And the other two candidates attacked Romney. At a rally in Des Moines, Sen. Rand Paul (R-Ky.), Ron Paul’s son, criticized Romney as flip-flopping on major policy issues.

“There is only one candidate who has never been accused of flip-flopping . . . my father, Ron Paul,” the younger Paul said to a crowd that chanted his father’s name.

And here in Polk City, Santorum disputed the notion that Romney’s experience as a corporate leader had prepared him to run the country.

An executive “assigns people who work for them. I can tell you, as a senator, I didn’t work for the president. Congress doesn’t work for the president,” Santorum said. “The American people don’t work for the president. It’s the other way around.”

Further back in Iowa’s pack, former House speaker Newt Gingrich (Ga.) seemed to be trying to soften his impending defeat. He appeared in Independence, Iowa, with Big Bud, the world’s largest tractor.

“I don’t think I’m going to win,” Gingrich said, blaming a barrage of negative ads from advocacy groups supporting Romney. “If you look at the numbers, that volume of negativity has done enough damage.”

But, he added: “Whatever I do tomorrow night will be a victory, because I’m still standing.”

One positive sign for Gingrich: He appeared to be recovering from a flu that had left him watery-eyed and lethargic over the past few days. At its worst, aides said, the candidate had to be kept quarantined on his own campaign bus. Gingrich’s wife, Callista, and aides kept their distance and used hand sanitizer.

Over the past few months, Iowa has embraced and then rejected four charismatic front-runners: Rep. Michele Bachmann (Minn.), Perry, Gingrich and pizza executive Herman Cain.

Now, the state seems set to split its vote among three candidates chosen, instead, for the ideas they represent.

For Romney, those are steadiness and electability. For Paul, they are small government and personal liberty. And Santorum’s appeal is based on his socially conservative views on issues such as abortion and same-sex marriage.

On Monday, the case for Santorum was made by surprise guests: the Duggar family, who have won reality-show fame because they have 19 children. Jim Bob Duggar, a former supporter of evangelical favorite Mike Huckabee, arrived in Polk City, Iowa, with 12 of his children in tow.

And he brought something the Santorum campaign hadn’t had until that point: a bus. The candidate’s shoestring operation had previously required him to trek around in a supporter’s pickup truck.

The Duggars’ massive white coach, parked outside a coffee shop where Santorum held an event Monday, said “Rick Santorum for President.”

“The mistake we made was the whole political candidate field was splintered last time,” Duggar said of 2008, when Huckabee won Iowa but could not translate the win to a national nomination.

“We’re calling on the Christian people throughout the United States to get behind Rick Santorum now, and don’t splinter the vote. Get behind a true conservative with a proven track record,” Duggar said.

The evidence of Santorum’s recent surge was obvious: The overwhelming crush of media at the Polk City stop included reporters from Italy and Australia. Dozens of actual voters — who two weeks ago probably could have snagged a private audience with Santorum — were now pressed out of the restaurant and stood outside in the cold. “I’m actually from Polk City,” said one to another as he was unable to squeeze his way inside. “Yeah, we don’t count,” the other responded.

Despite the sardine-like, fire-hazard quality of the crowd, Santorum followed a pattern established through 360 previous Iowa events. He took every question asked by voters (“One more question,” he said after speaking for about 30 minutes. “No?” he said, spotting more hands. “Two? Three more questions.”)

And he offered lengthy and at times in-depth responses. He said that his first executive order as president would be to ban federal funding for abortion and that American citizens accused of terrorism should have access to lawyers and courts, and he promised to push for a balanced budget amendment to the Constitution.

A few miles to the south, the two Pauls held a rally in the lobby of the downtown Marriott in Des Moines. The people in the packed ballroom included libertarians, disaffected Democrats, antiwar liberals, small-government conservatives, antiabortion activists.

“To me, he’s my Noah,” said Sharlene Dunlap of Des Moines. “He’s been saying there’s a flood coming for 30 years.”

On stage, Rand Paul said his father is the right man for these big-government times.

“Anybody here want their government to mind their own business?” Paul said, as the crowd erupted with a singular “Yeah!”

It took Ron Paul 30 years to matter in Iowa. Yet his son is already on the map in a big way — he is the first tea party senator. Which causes some to wonder where he might be headed next.

“Rand Paul is a chip off the old block; he stands for the same things Ron Paul stands for,” said David Kaniuk of Pleasant Hill. “If Rand Paul wanted to go for president, I would look into supporting him.”

And out came the father, refreshed and ready after a 36-hour break from the trail.

“Tomorrow is a very important day,” Paul said. “It’s small in numbers, big in importance.”

In the eastern part of the state, Romney began his day with a rally in a gymnasium in Davenport. He was joined by his wife, Ann, plus three of his five sons and his brother, Scott.

All hammered home the message that has helped Romney gain ground in Iowa.The main goal is beating Obama in November, they said. And Romney is the man to do it.

“I sense something happening as we’ve been going across Iowa,” Ann Romney told the crowd. “I sense a feeling, a coalescing, a momentum or whatever it is you want to call it, around Mitt. And I think people are starting to figure out that this is the guy that is going to beat Barack Obama.”

The biggest question of Tuesday night might not be who wins — Romney, Paul and Santorum would all gain momentum from a top-three finish — but who loses. And how badly.

For limping candidates such as Perry, Gingrich and Bachmann, a dismal showing could set off a chain reaction of bad news. Lower fundraising. Less advertising. And other disappointments in the upcoming primaries in New Hampshire and South Carolina.

Both Perry and Bachmann had relatively light schedules on Monday: three stops for Perry, two for Bachmann. Gingrich will have four events, including two in Davenport, where Romney made his case earlier Monday.

Staff writers Amy Gardner, Felicia Sonmez and Philip Rucker contributed to this report.