Whoever and whomever are both relative pronouns used to introduce /indicate dependent clauses just like who and whom respectively. Whoever and who( already discussed) are subjective pronouns( he, they) whilst whomever and whom ( also discussed) are objective( him, them).
When to use whoever/ whomever:
Look into the whoever/whomever clause, that is, the dependent clause they introduce. Ignore the independent clause.Then, assumingly replace the whoever/whomever with he or him respectively to see which one makes perfect sense. Choose that one!
Consider the following sentences:
1. I will not hesitate to award the contract to whoever/whomever merits it.
Let’s do the analysis of this sentence following the above procedure. The dependent clause in the sentence is: whoever/whomever merits it. I will focus only on it,ignoring the independent clause:I will not hesitate to award the contract. So let’s replace the whoever/ whomever with he/him.[ Remember: he =whoever, him=whomever]. After replacing, we have: he/him deserves it. And of course, you can’t say,“ him deserves it”. So, the right answer for the above sentence is whoever, not whomever. We say,
I will not hesitate to award the contract to whoever merits it.[he merits it]
2. I will award the contract to whoever/whomever the board chooses.
Let’s do as we did earlier. Replacing the whoever/whomever with he/him respectively in the dependent clause, we have: He/him the board chooses. Can you say,“ he the board chooses”? Rephrasing it, we have,“ the board chooses he”.Is this correct? Definitely not! For him, the sentence is: Him the board chooses. When we rephrase, it becomes,“ the board chooses him.” This is very grammatical; hence, whomever is the right pronoun to use, not whoever. We say,
I will award the contract to whomever the board chooses. [ The board chooses him]
3. Whoever/whomever is not against us is for us.
The dependent clause = Whoever/whomever is not against us. Replacing whoever/whomever with he/him, we have: He/him is not against us. And we can’t say him is not against us, but he is not against us. So whoever is the right choice.
4. Whoever/whomever Kate recommends will be employed.
[ Kate recommends he(whoever)? No, Kate recommends him.Whomever is therefore the right choice, not whoever]