WASHINGTON — Donald Trump is suddenly enamored of the rival nipping at his heels in the polls, ­saying he’d put Ben Carson in his Cabinet.

“Yes, I would, absolutely,” Trump told MSNBC when asked about the possibility on Friday.

But he said he didn’t know whether his fellow GOP presidential contender was a “tough negotiator” — the ultimate skill for Trump.

“I would say it’s not his wheelhouse,” Trump said. “But that I don’t know. But in certain elements of an administration, I think he would be very good.”

Carson is running a consistent second to Trump in national polls.