At GOP debate, Trump says 'stupid' U.S. leaders are being duped by Mexico

Speculation that Donald Trump would tone down his rhetoric on immigration and Mexico during the first prime time Republican presidential debate crumbled Thursday night when the outspoken billionaire made it clear that none of the candidates would be talking about immigration if it was not for him.

Trump has taken a particularly tough stance on immigration this summer, drawing criticism in the Latino community for saying Mexico was sending criminals and rapists to the U.S.

When asked by Fox News host Chris Wallace to provide evidence for his controversial comments, Trump fired back that U.S. Border Patrol agents have told him the Mexican government is sending criminals because they know the government in America is "stupid."

"They say this is what's happening because our leaders are stupid, our politicians are stupid," the real estate mogul said, during the debate inside Cleveland's Quicken Loans Arena. "And the Mexican government is much smarter, much sharper, much more cunning."

Trump added:  "They send the bad ones over, because they don't want to pay for them, they don't want to take care of them. Why should they, when the stupid leaders of the United States will do it for 'me?"

When asked to respond to comments made by former Florida Gov. Jeb Bush that he was "hurt" by Trump's comments about Mexicans and immigrants, the businessman-turned-presidential candidate did not turn to his left, where Bush was standing, but instead said the U.S. needs to build a wall and that he doesn't mind if it has a "big, beautiful door."

Immigration dominated a large portion of the first half of the debate, with most candidates pledging to take a tough stance on the issue -- but most of them disagreeing on how to fix a broken system.

Bush argued that border security is key to finding a solution to the immigration problem, but stuck by his stance that most undocumented immigrants come to the U.S. because they feel they have no other choice.

"I believe that the great majority of people coming here do it because they have no other option," Bush said.

Bush, whose wife was born in Mexico, added: "There's much to do. Rather than talking about this as a wedge issue, the next president will fix this once and for all, as a driver for high, sustained economic growth."

While Ohio Gov. John Kasich dodged an opportunity to criticize Trump on immigration – saying instead that Trump was "hitting a nerve in this country" -- other candidates were not so reluctant to pull any punches.

A seemingly confident Florida Sen. Marco Rubio took offense to Trump's assertion that Mexico is to blame for America's illegal immigration problem. Most immigrants coming illegally, Rubio said, are coming from countries such as Guatemala and El Salvador and are overstaying their welcome, as opposed to sneaking over the border.

Rubio said his Senate office takes phone calls frequently from people who entered the country legally but are frustrated with the slow legal immigration process and wonder if they should just come illegally.

"This is the most generous country in the world when it comes to immigration," he said.

But, in response to Trump, he said building a wall or fence won't solve the immigration issue.

"If (Mexican drug lord) El Chapo can build a tunnel under that fence, we need to deal with that," he said.

Texas Sen. Ted Cruz, who has not only praised Trump but even made a trip to New York to meet with him – struck a different chord Thursday evening by saying that he was one of the only candidates on stage who had not supported amnesty for undocumented immigrants.

In reference to Trump's comments calling U.S. leaders stupid, Cruz said: "It's not a question of stupidity, it's that they don't want to reform immigration."

The debate only included the top 10 candidates based on their showing in recent polls. The remaining seven candidates were relegated to a pre-debate forum, a low-key event in a largely empty arena, where candidates avoided debating each other and largely stuck to scripted responses on domestic and foreign policy issues.

The Associated Press contributed to this report.