Ben Carson, retired neurosurgeon and 2016 Republican presidential candidate, greets voters during a campaign stop in Spartanburg, S.C., during voting in the state's GOP primary. (Luke Sharrett/Bloomberg)

Armstrong Williams, one of Ben Carson’s closest friends and an informal adviser to his presidential campaign, said Sunday that the famous retired neurosurgeon faces a difficult decision in the coming days about whether to continue his bid for the White House.

“His supporters are asking him to stay in the race, and he is determined to fight on. But the voters have spoken pretty clearly in the first three states, and sooner rather than later, he’s going to have to think hard about whether he should keep doing this,” Williams said in an interview with The Washington Post. “He has a tough decision to make.”

Williams's comments came hours after Carson finished in last place in the South Carolina Republican primary with just 7.2 percent of the vote, and after Carson performed poorly earlier in the month in the New Hampshire and Iowa contests.

“We all want the best for him and he’s my brother,” Williams said of the mood within Carson’s inner circle. “The fact is, you have to look at these results and think through what the people out there are saying about what they want this year, about how they seem to want an angry nominee.”

Carson, however, is not convinced that a reevaluation is necessary, Williams said.

“He’s not yet convinced that Trump and Cruz are the choices the American people want. He thinks they may still wake up and rise again, and he wants to go to Nevada and pick up some delegates. I understand that, I get it,” Williams said. “This just may not be an election where somebody who doesn’t malign, who has honor and integrity, can win.”

He added: “Trump is gathering steam. The voters have shown that character isn’t everything. They want someone like Trump to stick it in the nose of the establishment of the media, to represent their anger and resentment. That’s the era we are in.”

Speaking to his supporters Saturday night, Carson vowed to head to Nevada, site of Tuesday’s caucuses, and he was scheduled Sunday to hold a “We the People” town hall at a casino in Reno, Nev.

"There are news people here who think I'm going to make a concession speech," Carson said. "This is a just the beginning speech."