When Ben Carson, the creationist neurosurgeon who wants to be president, overtook Donald Trump in some Republican polls in Iowa, the Donald accused his rival of a lack of energy.
"'Donald Trump falls to second place behind Ben Carson'," Trump read to supporters in Miami this weekend. "We informed Ben, but he was sleeping."
Carson, who like Trump has never held elected office, was given a chance to respond to the claims in an appearance on NBC's Meet the Press on Sunday.
I'm not sure that there's anybody else running who's spent 18 or 20 hours intently operating on somebody - I have plenty of energy.
But you know I am soft-spoken. I do have a tendency to be relaxed. I wasn't always like that. There was a time when I was very volatile. But I changed.
As a teenager, I would go after people with rocks and bricks and baseball bats and hammers. And, of course, many people know the story when I was 14 and I tried to stab someone.
The latter incident he refers to saw a teenage Carson try to stab a friend with a camping knife in an argument over a radio station. The knife hit his friend's belt buckle and snapped in half. Carson has said the incident changed his life.
Fortunately, you know, my life has been changed. And I'm a very different person now.