ANALYSIS: As Presidential Race Gets Bigger, Donald Trump Goes Smaller

PHOTO: Republican presidential candidates Jeb Bush, Sen. Ted Cruz and Donald Trump participate in a CBS News GOP Debate on Feb. 13, 2016, at the Peace Center in Greenville, South Carolina.PlaySpencer Platt/Getty Images
WATCH Nastiness Rises in Latest GOP Debate

It's often said that elections have consequences. This election is now of greater consequence -– and Donald Trump seemed not to have gotten that memo Saturday night.

The death of Supreme Court Justice Antonin Scalia raised the stakes of a presidential campaign that's now very literally about the future of all three branches of government. On a debate stage just hours after the stunning news broke, the Republican candidates agreed that President Obama shouldn't be allowed to tip the balance of power of the Supreme Court by nominating a new justice in his last 11 months in office.

Donald Trump, though, used the ensuing moments to rip into Jeb Bush –- in an exchange the Bush campaign probably couldn't have scripted better. Trump followed up with a later name-calling exchange with Ted Cruz, whom he called the "single biggest liar" on the stage.

First, Trump hurled insults at Bush and his supporters, mocking how much money his campaign has spent. He even went after Bush for bringing his mother out on the campaign trail with him –- and then attacked former President George W. Bush in a way that even few Democrats do.

"The World Trade Center came down during your brother's reign," Trump said, drawing boos from a crowd Trump had already dismissed as "Jeb's special interests and lobbyists." "That's not keeping us safe."

Bush fired back: "I'm sick and tired of Barack Obama blaming my brother for all of the problems that he's had. I'm sick and tired of [Trump] going after my family."

Marco Rubio came to the Bush family's defense: "I thank God all the time that it was George W. Bush in the White House on 9/11, and not Al Gore."

John Kasich summed up the back-and-forth: "I got to tell you, this is just crazy. This is just nuts."

Trump's fight with Cruz was even sharper.

"You are the single biggest liar. You probably are worse than Jeb Bush," Trump said of Cruz. "This guy will say anything. Nasty guy."

Cruz called Trump a liberal, and added this: "Donald, adults learn not to interrupt each other."

Predictions of Trump doing damage to his own campaign have been almost comically wrong over the past six months. Trump knows his followers, up to and including their antipathy for the Bush family.

But the Bush name still carries weight among South Carolina Republicans, in a story line that will be enhanced Monday with the expected campaign debut of George W. Bush. It's equally plausible to imagine Republicans growing sick of the name-calling, particularly as Scalia's death highlights the stakes of the race anew.

Bush was also able to rise above a sharp battle between Rubio and Cruz, on the now-familiar topic of immigration. They accused each other of misleading on their records; Rubio went so far as to say Cruz "doesn't speak Spanish," and Cruz offered to switch over to some "espanol."

Rubio picked up the anti-Cruz mantle, in a debate where he came out more aggressive -- and less repetitive -- than a week ago.

"This is a disturbing pattern now. For a number of weeks now, Ted Cruz has just been telling lies," he said.

The senator-on-senator violence left an opening for Bush to reference a recently departed candidate: "I feel like I have to get into my inner Chris Christie, and point out that the reason why I should be president is listening to two senators talk about arcane amendments to bills that didn't pass."

Kasich, again able to rise above most –- though not all -- of the sharpest exchanges of the night, essentially agreed: "We’re fixing to lose this election to Hillary Clinton unless we stop this."

Trump, of course, wasn't stopping –- not in a debate where he sought out fights with his rivals, notwithstanding his front-running status. Toward the end of the debate, he vowed to stop using bad words, which he said would be easy because he was "a very good student at a great school."

Perhaps Trump is indeed a better student than everyone in the political class has realized. That's been a recurring theme of this campaign, much to the frustration of his rivals.

But on a night where the importance of the race was highlighted anew, Trump’s rivals could portray him as flunking a big test.