I am bringing up a rather pedantic point here, but, one that has me completely stumped. This is going to require some serious grammar knowledge.
I was in a line at a shop today and the teenager at the counter actually said "May I please help whomever is next." As a matter of conversational English, I dare say, this construction borders on pretentious. But, on deeper thought, it might be fine in formal English since the subject of the dependent clause should typically agree with the main clause.
But, then I found the following post by Edwin Ashworth on this site regarding the issue:
If one wants to be pedantic, the correct version uses whoever rather than whomever in this construction as, though the accusative is required to agree with the main clause (Can I help John? Can I help him? Can I help him who is next? NOT *Can I help he who is next? - see Fowler), the compound lexeme whoever fulfils a dual accusative (relating to the main clause)/nominative (relating to the relative clause) role. Whomever fulfils a double accusative role (Treat whomever the acid came into contact with).
I followed Mr. Ashworth's explnation until he started making distinctions between dual and double accusatives (which I didn't think existed in English). If anyone could offer a clearer explanation, I would be apprecative. Thanks.