Donald Trump shakes hands with an overflow crowd after a rally Saturday at Dordt College  in Sioux Center, Iowa. (Evan Vucci/ AP)

SIOUX CENTER, Iowa -- With barely a week left until the Iowa caucuses, Donald Trump got defensive during a campaign rally in deeply conservative northwest Iowa on Saturday.

He defended himself against attacks other candidates have raised in television ads, including one from Sen. Ted Cruz (R-Tex.) that criticizes Trump's support of the use of eminent domain for development projects. He had an evangelical pastor from Texas vouch for him and his religious life, then told the crowd that he could be politically correct and eloquent if he chose to be, as he went to "the best schools." And he ripped apart the National Review, a conservative magazine that devoted its latest edition to 22 essays from conservative-thought leaders arguing why Trump should not be the nominee.

Trump said the "dying magazine" only attacked him to generate publicity as "it's failing, nobody reads it."

He read entire sections of a column written by Doug Ibendahl of Republican News Watch that tore apart the National Review's theme and explained why Trump has resonated with so many conservatives.

And he said the 22 essayists are "mostly losers" who have been making money by complaining about politicians without offering any solutions.

"These are conservative people -- which is good -- but they've been living off the trough, and where have they taken you? Look at who they've endorsed, look at the failures," Trump said, adding that Republicans should have won the White House during the past two elections. "Their attitude is wrong. You're not going to win with these people."

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One of the National Review essays was written by conservative radio host Glenn Beck, who endorsed Cruz on Saturday. Trump said Beck became "very hostile" because he was too busy to appear on his show.

"His show's failing, he's failing, he's always crying," Trump said, adding that he mostly dislikes criers. "I cried when I was 1-years-old. I was a baby. And my mother -- who's great, she was from Scotland -- she said: 'Even then, you didn't cry very much.' Okay, I don't want crying -- you know, I think crying's fine. But, I mean, I see this guy, and he's a sad sack. And he cries."

During the rally, Trump defended himself against the attack ads that have filled the Iowa airwaves. Trump said he has started to spend money on ads, but he doesn't want to overload viewers, as he already often dominates the news. Trump said he recently stayed in an Iowa hotel -- something he rarely does, as he often flies home to New York at the end of each day -- and had a chance to experience just how saturated the airwaves have become.

"I'm watching all of these ads: I'm watching them for Carson, I'm watching them for Rubio, I'm watching them for Cruz," Trump said. "I'm watching all of these ads. I don't want to take a chance because you may believe some of those ads -- by the way, those ads are total bulls---, okay? I'm watching these phony ads."

Trump defended himself against some of the arguments raised in some of the ads, including one from Cruz that criticizes Trump's support of the use of eminent domain.

"Let's talk about eminent domain," Trump said. "Eminent domain is a power used by government so that it can take land for highways, for roadways, for schools, for hospitals, for different things -- for government, whether it's city, state, federal -- for pipelines."

Trump then seemed to start to say that the conservatives who have been "living off the trough" are trying to make an issue out of what he considers a non-issue, but he did not complete the thought before launching into his attack on the National Review.

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At the rally, Trump continued to raise questions about Cruz's eligibility to be president, as he was born "on Canadian soil" to an American mother and Cuban father. At one point Trump wondered aloud if he should challenge Cruz's eligibility by suing.

"Should I do it just for fun? Should I do it?" Trump said. "It's so nasty though -- oh, I'm so good at that stuff. It's so nasty."

Trump also tore into former Florida governor Jeb Bush, as he does at nearly every rally. Trump mentioned one of Bush's attack videos that features Democratic front-runner Hillary Clinton -- likely the one that forecasts Trump winning the nomination but losing in the general election to Clinton, then tweeting his concession speech.

"It's like a Hillary Clinton ad -- it's a great ad for Hillary Clinton," Trump said. "What the hell is -- I mean, this guy. I don't think he's a smart person, I'll be honest with you."

Trump also referenced a Bush video message sent to supporters that features former first lady Barbara Bush taking this subtle dig at candidates like Trump: "When push comes to shove, people are going to realize Jeb has real solutions, rather than talking about how popular they are, how great they are." On Friday night, Trump and Bush got into a Twitter fight about the video, and Trump kept it going on Saturday.

"His mother is a nice woman, but he uses his mother, and I said: 'Jeb, ISIS doesn't want you to be using your mother. They want to deal with you, Jeb... You're going to have to get out there yourself, Jeb,'" Trump said, each time emphasizing "Jeb," as if he were reading it off a Bush campaign sign that puts an exclamation point after the candidate's first name. "Weak. Weak, pathetic people. Low-energy is a better term."

Trump wrapped up his 65-minute speech with a plea for Iowa to stop its trend of picking Republicans that do not go on to become president.

"Iowa hasn't had a winner in 16 years -- you've picked a lot of losers, folks," Trump said, as the crowd laughed. "You've picked a lot of losers. You have picked a lot of losers. You've got to get back on the ball... If you vote for Ted Cruz, you're not going to win. You're not going to win."