How do polls affect presidential elections?
polls voters research information about each of the candidates.
polls tell voters the issues that candidates support.
polls identify the top candidates and the media interview those candidates.
polls explain which candidates should win the election.

The best answer from the options given, to the question: How do polls affect presidential elections, would be: Polls identify the top candidates and the media interviews those candidates.

Explanation:

Polls are a means by which elections can be affected and swayed in favor of a candidate, a political party, or a group, because they tend to show the upward trends, which means, it will display, in a campaign, who is at the top in voters´ intention to vote, and thus, might sway other voters to choose either of those at the top. When a campaign takes place, especially for elections, researchers, and pollers, seek to help the public to make the better choice by finding out who is leading the intention of vote in voters. By doing this, polls may allow the public to know who has a chance of being elected, and thus sway support from the public to one, or another of those candidates. The media, of course, will focus their interviewing efforts on those who stand a chance of being elected. Which is why the answer is the one above.

because the early people found out about it.