It can be important since it makes a big difference in a close race, and a mainstream candidate loses (or wins) when the majority normally would have elected the other one.
Speedy is the adverb in the sentence.
Adverbs are words used to modify adjectives, verbs, etc in the sentence. They commonly end with the letter 'y'. Examples include slowly, loudly, easily, quite, and soon.
The King believes that Englishmen must be "the most pernicious race of little odious vermin that nature ever suffered to crawl upon the surface