The ninth Republican debate was the nastiest. Gone were the early debate focuses on pointing out differences with Hillary Clinton and Bernie Sanders. This was hand-to-hand combat on Saturday night with no insult unsaid.

“You are probably worse than Jeb Bush. You are the single biggest liar,” Donald Trump told Ted Cruz after the Texas senator referred to the real estate mogul’s penchant for backing liberal positions. “This guy will say anything. Nasty guy. Now I know why he doesn't have one endorsement from any of his colleagues."  

Cruz responded: “Donald didn't disagree with the substance that he supports taxpayer funding for Planned Parenthood. And Donald has this weird pattern-- when you point to his own record he screams, ‘liar, liar, liar,’” Cruz said.

Trump then turned his fire on Jeb Bush, channeling liberal criticism of George W. Bush as a liar – channeling attacks that normally aren’t heard outside of Democratic fringe meetings.  "The World Trade Center came down during the reign of George Bush. He kept us safe? That is not safe.” 

Marco Rubio gained points by joining Jeb in defense of his brother.

But Rubio later stumbled in taking a swipe at Cruz’s immigration record.  He parried Cruz’s criticism of a Rubio interview on Spanish-language Univision by claiming “I don't know how he knows what I said on Univision because he doesn't speak Spanish." Cruz quickly responded by speaking in Spanish with little trace of an Anglo accent.

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All of the candidates proved adept at avoiding the solid questions from CBS’s John Dickerson and Major Garrett accompanied by the Wall Street Journal’s Kimberly Strassel. 

John Kasich avoided questions about his Medicaid expansion record in Ohio. Cruz sidestepped a question about his tax plan.

But the most telling evasion came when Trump declined to name anyone around him who will tell him he is wrong -- other than his wife on unspecified topics.  

Overall, Trump’s performance Saturday night was vintage Trump -- just at greater volume and with much more interrupting and swipes at the audience.  

Several observers say Trump was at his least presidential in Saturday's debate. I doubt that will hurt him with his cadre of followers. He seems to have a solid hold on about 25 to 35 percent of the GOP electorate. But his bellowing and often buffoonish exchanges make it clear he is likely going to have difficulty raising that ceiling. 

He is a frontrunner who has forgotten that you have to find ways to raise the ceiling on the potential number of votes you get.  

A candidate has to win a majority of delegates to the GOP convention, not a plurality. The best analysis is that even with a few states holding winner-take-all primaries, the eventual GOP nominee will have to win over 45 percent of the vote by the end of the primary season.

With each debate, Trump excites his fans, worries his skeptics and makes it a little harder for folks in the middle to accept him as a true conservative who can win in November.

John Fund is a columnist for National Review. Follow him on Twitter @JohnFund.