The purpose of poll watchers is to

a.
make sure that only qualified people vote.
b.
kept supporters of opposing candidates from voting.
c.
allow only their party's supporters to vote.
d.
allow everyone to vote.

freedom of speech is also protected by the 1 amendment.

explanation:

here is pretty much what the 1st amendment says:

congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.