Bribing/Buying Votes

If you have a Diplomat in another nation’s capital, you’ll be able to deal with it for support in the World Congress. If they agree, the nation will use their “core” delegation (but not the City-State delegates) to support you in the next vote. Note that bribing deals work exactly the same way as other deals – you can exchange resources or  Gold (or anything else you can) for their support for a specific proposal you choose.

https://civilization.fandom.com/wiki/Diplomatic_victory_(Civ5)