|Your words won't cut this mustard either!|
What does a speechwriter do? Write speeches, obviously. There's more to it than that, though. Political speeches aren't expected to be as eloquent as Shakespeare, but we highly doubt anyone would be elected into office nowadays without the help of carefully selected words, meticulously constructed sentences and organised paragraphs.
The speechwriter will have to write drafts for their clients and, much like a copywriter, accept criticism and be willing to redo and redraft their work. The difference is that they're writing with the aim of their words being spoken rather than being read. They have to be aware of the speaker's speech tendencies. They'll need to avoid sounds that the speaker is uncomfortable saying as well.
The speechwriter is anonymous, of course. They can't take credit for writing a speech since it could undermine the person who is reciting it. We are, after all, listening to them and not the speechwriter. A speechwriter works in a very similar capacity to a ghostwriter... they accept little to no credit for their work and write speeches in such a way that they appear to have been written by their client. They're unsung heroes of the writing world!