What is the ruling on praying behind an Imam who coughs and clears his throat during prayer?

Clearing one's throat during prayer does not invalidate it. There are three opinions regarding this: it never invalidates it, it always invalidates it, or it invalidates it unless done for a valid excuse. The first opinion is the most correct, because clearing one's throat does not fall under the category of forbidden speech in prayer. Based on this, the prayer of an Imam who cleared his throat is valid, and there is no harm in praying behind him.