Republican frontrunner Mitt Romney was heckled repeatedly during his closing rally of the Iowa campaign, with shouts that he is ignoring the poor and is too close to Wall Street.
The protests came as the candidates made their closing arguments before Tuesday's Iowa caucuses, the first of the contests to choose a Republican to take on Barack Obama for the White House.
The protesters were from the Occupy movement, which has engaged in a series of disruptive events round Des Moines over the last week.
Romney refused to be flustered by the protesters, saying they had a right to express their views, but he brought his speech to an abrupt end soon afterwards, possibly to avoid any further disruption. He told the protesters he hoped they would make the same "noise" if Obama visited Iowa.
Before the protests he had focused his speech on criticizing Barack Obama and avoided any criticism of the rival Republican candidates, a sign of his increasing confidence of a good outcome in Tuesday's Iowa caucuses.
Romney's rally at a warehouse in Clive, on the outskirts of Des Moines, did not match the crowds Obama attracted four years ago but it was bigger than any of the rallies held by his Republican rivals.
At an earlier event on Monday in Cedar Rapids he risked sounding overly triumphant when he predicted victory. His comment also dangerously raised expectations so that second place would be viewed as a failure. He told a crowd of about 500: "I need a great showing here in Cedar Rapids. We're going to win this thing with all our passion and strength and do everything we can to get this campaign on the right track to go across the nation and to pick up the states and to get the ballots I need and the votes I need to become our nominee."
His campaign team attempted to undo the damage by saying the "thing" he was referring to was the nomination, not the Iowa caucuses.
More than 120,000 voters are expected to turn out to vote in the caucuses.
The candidates basically turn over the campaign on Tuesday to the armies of volunteers recruited to get supporters to the gyms, schools, community centers and other voting locations.
Newt Gingrich, who had been leading Romney in the polls, did not help his chances of revival with another fumble for which he apologized to supporters in Davenport on Monday night. He had suggested earlier in the day that he could not win. Even a hint he does not expect to win makes it harder for his volunteers to get wavering supporters out to vote.
Attempting to explain his fumble, he said:"I made the amateur mistake of having two compound sentences."
Earlier in the day he had said: "I don't think I'm going to win. If you look at the numbers I think that volume of negativity has done enough damage. On the other hand, if the Des Moines Register is right in its 41% potentially undecided, who knows what's going to happen."
If Gingrich continues to fall, Texas governor Rick Perry could be the beneficiary, possibly nicking the fourth place slot. Polls show Romney in the lead, followed by Ron Paul, Rick Santorum and Rick Perry.
Perry, the Texas governor, has consistently underperformed since joining the race in August. His closing rally in the town sharing his name – Perry – was slick, opened by a country and western singer, with two popular Republican governors, Bobby Jindal of Lousiana and Sam Brownback of Kansas, to introduce him.
But the Texas governor, in spite of all the money behind him, is not a natural orator. The crowd was small compared with Romney's and, so far, he is not attracting much media interest.
Perry predicted he would win but, like Romney, did not specify whether he was talking about Iowa or the nomination. Polls suggest he is lying in fifth place behind Romney, Ron Paul, Rick Santorum and Gingrich.
But Robert Haus, Perry's campaign co-director in Iowa, said: "I think he is going to surprise people. Our crowds have been good over the last month. People are still making up their mind.
"I think our organization is second to none. We may not be flashy but we are getting it done. I know we will finish in the top four."
Perry's organization, backed by 500 volunteers who have come from 36 other states, is superior to Gingrich's and that might see Perry pip Gingrich to the fourth spot.
If Perry were to secure a fourth spot he might yet revive his campaign, which so far has been a spectacular flop, and be in contention with Romney by the time they reach Florida at the end of the month.