It's unlikely that Bernie's performance in the South Carolina debate affected him in any way.  Those who support him will continue to do so; those who fear him will also continue to do so.

First, some global observations about Bernie's debate performance.  Bernie is very good at demagoguing.  No matter the question, he goes off on his shtick about the need for socialized medicine so everyone can have the "right" to health care.  What he consistently ignores is that America has the best outcomes in the world.  All the other countries offer is the boast that people can see doctors, not the boast that they can get treated.  This is just one of Bernie's many subtle lies, where he makes ideological statements that are not borne out by the facts.

Bernie also constantly repeats his riff about 500,000 homeless people, ignoring the fact that those homeless people are the result of Democrat policies.  They're the result of Democrats doing away with institutionalizing the mentally ill; they're the result of Democrats failing to crack down on drug use and sales; they're the result of Democrats making marijuana, a gateway drug, socially acceptable; and they're the result of blue-city policies that are a Petri dish for homelessness, insofar as offering free food, free shelter, free needles, and freedom from consequences for the antisocial behaviors that accompany drug use.

Finally, Bernie endlessly repeats his promise for free college education and student loan forgiveness.  The reality is that America doesn't need more people with sociology and queer studies degrees.  It needs more people who can do useful things — fix cars, fix plumbing, rewire a house, and build a house.  It needs fewer institutions of indoctrination that teach less than ever but have burgeoning administrations serving identity politics while driving costs ever upward.  The vast number of Americans who opted to pay for college or to skip four years of extended adolescence in favor of work also should not have to pay for adults who willingly took on debt they had no reasonable belief they could ever pay.

All of Bernie's demagoguery, which he repeated endlessly during the debate in South Carolina, should be acknowledged as fraudulent and dismissed.

More specifically, these were the highlights and lowlights of Bernie's debate:

Bernie repeatedly attacked billionaires.  Now that he's a millionaire, he has nothing to say against them.  Those who support class warfare forgive him for his hypocrisy, and those who don't support class warfare laugh at him.

Bernie continued to be opaque about his spending and how he intends to pay for it.  He won't admit that his plans will cost close to $100 trillion over ten years.  He promises that socializing medicine will bring costs down because we have too many insurance companies (just as we have too many deodorant brands).

On guns, Sanders conceded he was wrong when he refused to vote yes on a law imposing liability on gun manufacturers and then boasted about his current D- from the NRA.  On a stage of people fanatically opposed to the Second Amendment, though, he looked weak.  Republicans should point out that when Bernie was a low-level Marxist revolutionary, he wanted guns; now that he has power within his grasp, he wants to disarm the American people.

When asked about making health care more affordable to people in rural areas, Bernie said he worked with Sen. Clyburn (D-S.C.) to increasing funding for rural programs under Obamacare.  Like the rest of the people on the stage, he shied away from the fact that Obamacare killed rural hospitals.  He also assured voters that his Medicare for All (AKA socialized medicine) would solve the rural care problem.  Presumably, once doctors have no profit incentive, he plans to force many of them to work in areas they would otherwise prefer to avoid.

The moderators and the other candidates attacked Bernie for praising policies in China, Cuba, and Nicaragua.  Bernie responded that while he opposes authoritarianism, he just loves what the authoritarians get done (literacy, socialized medicine, etc.).  And no, he didn't use those precise words, but that's the gist of what he said.

Bernie's most shocking statement was calling Bibi Netanyahu a "reactionary racist."  Clearly, Bernie has found his happy place with the rising crowd of anti-Semites in the Democrat Party.

Aside from being more open about his hatred for Netanyahu, Bernie didn't say anything unexpected.  He spoke in his usual hectoring monotone; he showed his continued disdain for America; and he made clear his desperate desire to mold America into another Cuba, Nicaragua, or Soviet Union, only with himself in power instead of some mean foreign authoritarian dictatorship.