Defeats the incumbent

• Usurps
• Votes out
• Ousts, in a way
• Bests, as an incumbent
• Beats, as an incumbent
• Chairs in the General Assembly?
• Throws from a saddle
• Defeats, in a way
• Defeats in a way

Wiktionary Word definitions in Wiktionary
vb. (en-third-person singular of: unseat )