The "undercard" debate was much less explosive, with most of the back-and-forth coming from an argument between New Jersey Gov. Chris Christie and Louisiana Gov. Bobby Jindal . Those two governors disagreed over whether the Republicans need a candidate who is best positioned to defeat a Democratic opponent, or if conservative economic adherence is the most important attribute.

Sparks flew on immigration and defense spending in the fourth Republican debate Tuesday night, but few candidates came away as an obvious winner.

Chris Christie



Just as Fiorina made a case for joining the top-tier of candidates when she successfully dominated the first GOP undercard debate, many pundits said the New Jersey governor successfully justified his presence at the main event next time around.

When Jindal criticized New Jersey's economic record, Christie refused to punch down, turning every question to Democratic front-runner Hillary Clinton.

"I saw the most disgraceful thing I've seen in this entire campaign a few weeks ago: Hillary Clinton was asked the enemy she's most proud of, and she said Republicans," Christie said in his closing comments. "In a world where we have Al-Qaeda and ISIS, the mullahs in Iran and Vladimir Putin, the woman who asks to run and represent all of the United States says that her greatest enemies are people like you in this audience and us here."

For what it's worth, CNBC's unscientific online poll found that 62 percent of readers said Christie had won the early debate, as of midnight ET.

Conservative tax policy



Significant differences arose during the night's discussions of immigration, banking regulation and foreign policy. There was little argument, however, on the topic of taxes, as candidates' plans all pointed in the same direction for the country.

"What I notice most in this debate is that all the candidates agree that we need tax reform that lowers marginal tax rates to create jobs. All the candidate's plans allow expensing for business investment and a territorial tax system," anti-tax crusader Grover Norquist told CNBC in an email as the debate wrapped up. "The tax debate shows the consensus that exists in the Republican Party on tax reform...something that was not true in 1980 or 1990."

As for specific candidates, Norquist highlighted Trump's proposed 15 percent corporate rate, which "set the pace."

"Consensus used to be to cut the corporate income tax to 25 percent....now 15 percent is the new 25 percent," he added.