Carson argued he's spent his life making life-or-death operating calls instead of attending swanky parties and raised campaign cash in an appearance on ABC's "This Week" on Sunday.
"There's no question as I haven't spent a lot of time schmoozing and asking for big money and going to cocktail parties, but I've spent many a night in the operating room -- cold, sterile place with a little child's life on the line working very hard to preserve that," Carson said.
"You know, it's a very different kind of experience," he said. "Lots of 2 a.m. in the morning calls and making snap decisions on what needs to be done."
Carson's comments come after Cruz had questioned support for both Carson and Trump at a private donor event, according to audio leaked to The New York Times
"Who is prepared to be a commander-in-chief? Who understands the threats we face? Who am I comfortable having their finger on the button," Cruz said. "Now that's a question of strength, but it's also a question of judgment. And I think that is a question that is a challenging question for voters."
It's an escalation of a fight between the two candidates that comes as polls in Iowa and nationally show Cruz picking up Carson's support as the retired brain surgeon -- once briefly the GOP's front-runner -- sinks to fourth place, behind Donald Trump, Cruz and Florida Sen. Marco Rubio.
While Carson took aim at Cruz on Sunday, a bigger fight between Cruz and Trump has also been brewing.
Trump countered Cruz's assertion that he can't match Cruz's judgment as well, recounting to CNN's Jake Tapper on "State of the Union"
a list of examples he believes he's had better judgment.
"I was against going into Iraq," Trump told Tapper in an interview that aired Sunday on "State of the Union." "That's good judgment. I was for bombing (ISIS's) oil long before anyone else was talking about it. That's good judgment. I have great judgment. I would say I have far better judgment than Ted."
Cruz had told donors in the leaked audio that he believes "gravity will bring both of those campaigns down." He acknowledged, though, that he hasn't been publicly critical of Trump.
Cruz described his strategy by saying: "So my approach, much to the frustration of the media, has been to bear hug both of them, and smother them with love."
Still, Trump said the two must inevitably clash, even though Cruz has been "so nice to me."
He predicted he'll outlast Cruz "because I'm more capable. Because I have a much better temperament. Because I actually get along with people much better than he does."
Those battles are likely to come to a head when the candidates meet in person Tuesday night for CNN's Republican presidential debate in Las Vegas.