MILWAUKEE (CBSNewYork/AP) -- Eight Republican candidates once again faced off -- and traded shouting matches -- for the GOP's fourth presidential debate Tuesday evening in Milwaukee.
This time, organizers said issues would be limited to the subject of the economy, "nothing more and nothing less."
The debate came on a day that workers across the nation were demanding a nationwide increase in the minimum wage to $15 per hour, while Gov. Andrew Cuomo's office announced that about 10,000 state employees will see their minimum wage pay increased to $15 in the next six years.
The candidates were not sympathetic to a minimum wage increase. Even though he has advocated for eliminating federal income taxes for low-income earners, real estate mogul Donald Trump said he cannot support an increase in the minimum wage.
He said taxes and wages are all too high for the U.S. to be competitive in the world.
"We are a country that is being beaten on every front – economically, militarily – there is nothing we can do now to win. We don't win anymore," he said.
Carson said he believes the minimum wage causes problems rather than solving them.
"People need to be educated on the minimum wage," Carson said. "Every time we raise the minimum wage, the number of jobless people increases."
Carson said he had worked as a lab assistant and had held several other jobs as a young man – and he would not have gotten those jobs if his employers had had to pay him "lots and lots."
He said the question should be "how do we allow people to ascend the ladder of opportunity, rather than how do we give them everything and keep them independent."
U.S. Sen. Marco Rubio (R-Fla.) also said a high minimum wage is bad for the economy.
"If you raise the minimum wage, you're going to make people more expensive than a machine," he said.
Rubio said more efforts should be made to ensure that people have opportunities and move up. He pointed specifically to support for vocational training.
"Welders make more money than philosophers," Rubio said. "We need more welders and less philosophers."
Democratic front-runner Hillary Rodham Clinton has called for raising the minimum wage from $7.25 an hour to $12. Her chief rival, Vermont Sen. Bernie Sanders, has backed an increase to $15.
As CBS2's Tony Aiello reported, the issue of immigration lit the fuse among the candidate a short time later.
Trump again defended his call for building a wall and removing undocumented immigrants en masse – prompting a criticism from Ohio Gov. John Kasich that such a plan was not realistic.
Kasich said in 1986, President Ronald Reagan had said undocumented immigrants had been allowed to stay, and the real problem was that the border has been poorly controlled.
But to ship 11 million people out of the country, "and somehow pick them up at their house and ship them out to Mexico? Think about the families. Think about the children," Kasich said.
Trump retorted by talking about a president from nearly twice as long ago. He said President Dwight David Eisenhower removed 1.5 million undocumented immigrants from the country, and finally had them deported far, far away from the U.S. border when they kept coming back.
"Dwight Eisenhower – you don't get nicer. You don't get friendlier," Trump said. "They moved a million and a half people out."
U.S. Sen. Ted Cruz (R-Texas) said that critics who do not take illegal immigration seriously as a problem are not experiencing the economic hardship he said it causes for American workers.
"If a bunch of people with journalism degrees were coming over and driving down the wages in the press," the media would take illegal immigration more seriously, Cruz said.
Meanwhile, a feisty former Florida Gov. Jeb Bush sought to regain his footing, challenging President Barack Obama's economic record and criticizing Democratic front-runner Hillary Rodham Clinton for pledging to build on his policies.
``It may be the best Hillary Clinton can do, but it's not the best America can do,'' said Bush, who is attempting a campaign reset after a sluggish start to his bid for the GOP nomination.
On the subject of federal taxes, Carson was asked further about his flat tax proposal that he has compared to "tithing," as compared with Trump's plan in which higher earners would pay more.
Carson said his plan called for everyone paying the same proportion, and, "I don't see how anything gets fairer than that."
He also said all deductions and loopholes would be eliminated, and disputed the claim that eliminating deductions mortgage payments and charitable donations would reduce people's overall spending power.
"People had homes in 1913 before we introduced the federal income tax" and later started deductions, he said.
Cruz and U.S. Senator Rand Paul (R-Ky.) also defended flat tax plans. Cruz's plan would also eliminate many taxes and abolish the IRS, which he said would make for tremendous economic growth felt by everyone.
Carson also faced questions about the veracity of his celebrated biography, which has been at the center of his connection with voters. Carson pushed back on the questions and suggested the media were harder on him than Clinton.
``We should vet all candidates,'' Carson said. ``I have no problem with being vetted. What I do have a problem with is being lied about.''
While pieces of Carson's background had been challenged earlier in the campaign, the questions ballooned last week after CNN reported it could not find friends or confidants to corroborate the story, told in his widely read autobiography, of his unsuccessfully trying to stab a close friend when he was a teenager.
On the subject of health care, businesswoman Carly Fiorina says as a cancer survivor she knows better than anyone the importance of people with pre-existing conditions having access to health insurance.
Fiorina brought up her own battle with cancer when talking about her plans for health care reform during the fourth Republican presidential debate Tuesday in Milwaukee.
She said the health care overhaul law championed by President Barack Obama ``is failing the very people it's designed to help.''
Fiorina said the law needs to be repealed to let states manage high-risk pools while allowing the free market to work.
She said, ``Let us try the one thing in health care we've never tried -- the free market.''
Trump and Carson are fighting to maintain their place atop the polls, while others, including former Bush, are fighting for their political survival.
According to a new McClatchy-Marist Poll out Tuesday, Carson and Trump are virtually tied heading into the debate with Carson at 24 percent and Trump at 23 percent.
Rubio is in third place with 12 percent followed by Cruz and Bush, who are both in fourth place with 8 percent.
Missing from the lineup were New Jersey Gov. Chris Christie and former Arkansas Gov. Mike Huckabee. Both were dropped from the top-tier debate with low poll numbers in national surveys, sparking criticism for the way networks hosting the debates have determined participation.
Christie and Huckabee instead appeared in an undercard debate, along with Louisiana Gov. Bobby Jindal and former Pennsylvania Sen. Rick Santorum.
"We're not whiners and moaners and complainers in the Christie campaign,'' Christie said on Fox News. "Give me a podium, give me a stage, put the camera on, we'll be just fine.''
Debate host Fox Business Network earlier promised to focus on substantive issues, a response to those who accused last month's CNBC debate of focusing too much on politics and "gotcha'' questions.
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