Muscatine, Iowa(CNN) Donald Trump spent his Sunday on the stump ripping his political rivals and urging his voters to trek to the caucuses, all the while predicting victory in the Iowa caucuses taking place in just eight days.
Speaking to supporters in a crowded high school gym, Trump focused the brunt of his attacks on former Florida Gov. Jeb Bush, whose campaign launched attack ads against Trump, and on Texas Sen. Ted Cruz, who is neck-and-neck with Trump in the latest Iowa polls. Trump's speech came after he attended Sunday church services at the First Presbyterian Church in Muscatine.
"It's time to give up, Jeb. It's time to give up," Trump said, noting that he only mentioned Bush because of the negative ads. "In life, sometimes you have to admit it when you don't have it."
Trump also harped on his chief Iowa rival, Cruz, for his opposition to ethanol mandates.
"Cruz is getting oil money. He is so against ethanol, you can forget it," Trump said, referencing Cruz's position in favor of phasing out the mandated ethanol fuel levels in gasoline, which are a boon to Iowa's economy.
Trump also once again raised the issue of Cruz's Canadian birthplace, which has become a staple of the New York billionaire's stump speech -- with Trump suggesting that Cruz does not meet the constitutional requirement that the president be a "natural-born citizen."
And of course, Trump didn't spare the Democrats running for president, knocking both former secretary of state Hillary Clinton and Vermont Sen. Bernie Sanders.
Trump even took credit for Sanders' recent rise in the polls versus Clinton in the early states of Iowa and New Hampshire, suggesting that his attacks against Clinton helped buttress the surging senator's rise.
"I was the best thing that happened to Bernie," Trump said of Sanders, whom Trump said he would love to face in the general election.
"She went down and he got all the credit for it," Trump said.
Trump's speech on Sunday was also interrupted by a pair of protesters who held up a banner reading "STOP HATE."
As the protesters were escorted out of the event, Trump remarked on one of the protesters, who was wearing a red turban, similar to those members of the Sikh religion wear.
"He wasn't wearing one of those hats was he? Was he wearing one of those?" Trump said. "And he never will. And he never will. And that's OK because we have to do something. It's not working."