“The question of confronting a challenge and sticking with it and having a backbone, if you will — he’s never been challenged in his life in that regard. He’s young,” Bush said during an interview for the “Off Message” podcast to be posted in its entirety on Monday morning — and vowed to stay in the race despite a whisper campaign by Rubio backers to nudge him out after next Tuesday’s primary here.

“The Rubio people have made an argument that, ‘I came in third. Everybody else must leave,’” he said. “I’m not buying it. Why should I? … You know, it’s like come on. You get a bronze, you get a little red ribbon, and everybody is supposed to just — the waters are supposed to part?”

Bush, who garnered about 3 percent in the Iowa caucuses, is in the political fight of his life after starting the campaign with a huge cash advantage, pick-of-the-litter staff and establishment support.