sell someone down the river

sell (one) down the river

To betray someone's confidence. These companies all want to pretend like they're your friend, but they'll sell you down the river the moment it makes financial sense for them. Part of the discontentment among voters comes from the sentiment that those in government sold them down the river when the economy collapsed.
See also: down, river, sell

sell someone down the river

If someone sells you down the river, they betray you or do something which harms you in order to gain an advantage for themselves. He has been sold down the river by the people who were supposed to protect him. He said he could not agree to measures which would sell British farmers down the river. Note: This is a reference to slave-owners on the Mississippi river selling unwanted slaves to other slave-owners further down the river, where the conditions were harsher.
See also: down, river, sell

sell someone down the river

betray someone, especially so as to benefit yourself. informal
This expression originated in the USA, with reference to the practice in the slave-owning states of selling troublesome slaves to owners of sugar-cane plantations on the lower Mississippi, where conditions were harsher than those in the more northerly states.
1998 Bookseller Once you have lost it with the first three the last lot will sell you down the river so fast it isn't true.
See also: down, river, sell