They would jump on a bullet for him

This was uttered when discussing the blind loyalty of Trump supporters.  It is a congruent conflation of “take a bullet for (someone)” and “falling (or jumping) on a grenade for (someone)”, both meaning to accept a personally harmful or sacrificial task to protect someone else.  Jumping on a bullet doesn’t seem like a great sacrifice to me, so perhaps this speaker was not such a loyal follower.  A big thanks to John Kooser for hearing this one.