sell someone down the river
US /sel ˈsʌm.wʌn daʊn ðə ˈrɪv.ər/
UK /sel ˈsʌm.wʌn daʊn ðə ˈrɪv.ər/

1.
裏切る, 見捨てる
to betray someone for one's own benefit, especially someone who trusts you
:
•
I can't believe he would sell me down the river after all we've been through.
私たちが経験したすべての後で、彼が私を裏切るなんて信じられない。
•
The politician was accused of selling his constituents down the river by voting against their interests.
その政治家は、有権者の利益に反する投票をすることで、彼らを裏切ったと非難された。