* Whoever is used as the subject of a verb or as the nominative case in a clause. It's the equivalent of "he who" or "she who."
* Whomever is used as the object of a verb or preposition, or as the objective case in a clause. It's the equivalent of "him who" or "her who."
Here are some examples:
Whoever:
* Whoever wins the election will face a difficult challenge. (Subject of the verb "wins")
* Whoever you choose to go with, make sure they are trustworthy. (Subject of the verb "choose")
* Whoever leaves the door open will get a talking to. (Subject of the verb "leaves")
Whomever:
* I will support whomever the party nominates. (Object of the verb "support")
* He will talk to whomever wants to hear him. (Object of the verb "talk to")
* I gave the book to whomever was standing by the door. (Object of the preposition "to")
Tip:
To remember when to use "whoever" and "whomever," try substituting "he/she" or "him/her." If "he/she" fits, use "whoever." If "him/her" fits, use "whomever."
For example:
* I will support he/she the party nominates. (Incorrect, use "whomever")
* He will talk to him/her wants to hear him. (Incorrect, use "whomever")