WASHINGTON — Sinking poll numbers would be the one thing to force Donald Trump out of the presidential campaign, he said Thursday.

Asked whether he’d quit if he could no longer boast he’s “leading in every poll,” Trump told CNBC: “Well, I’m not a masochist.

“If I fell behind badly, I would certainly get out. I’m in this for the long haul.”

The RealClearPolitics average of recent national polls has Trump at 23 percent, ahead of Ben Carson’s 16 percent. They are followed by Carly Fiorina (12 percent), Sen. Marco Rubio (10 percent) and Jeb Bush (9 percent).

Trump also continues to dominate Facebook, where nearly 22 million people generated more than 94 million “interactions” about him between Aug. 30 and Sept. 29.

Carson trailed Trump with 27.6 million interactions by more than 6 million people.