4. (U.S. Politics) To refuse to support a nomination made by a party or a caucus with which one has been connected; to break away from a party.
Bolt, adv. In the manner of a bolt; suddenly; straight; unbendingly.
[He] came bolt up against the heavy dragoon.
Thackeray.
Bolt upright. (a) Perfectly upright; perpendicular; straight up; unbendingly erect. Addison. (b) On the back at full length. [Obs.] Chaucer.
Bolt, n. [From Bolt, v. i.] 1. A sudden spring or start; a sudden spring aside; as, the horse made a bolt.