set (someone/something) against (someone/something)

to cause one person or group to oppose another.

His health-care plan would divide older Americans and set senior against senior.

The disagreement has turned into a public feud that has set members against each other.

• on coat-tails
• on course
• on cue
• on dangerous ground
• on deck
• on demand
• on doorstep
• on duty
• one after the other
• one and all
• one and the same
• on earth
• one day
• one-day wonder
• on edge
• one for the books
• one for the road
• One good turn deserves another.
• one-hit wonder
• one-horse race
• one-horse town
• one-man band
• One man's meat is another man's poison.
• on end
• one-night stand