By shoving polls in the public's faces, you make them support the frontrunners.
I'll explain that in detail...
the media tells you that Obama/Clinton/McCrazy are at the top of the polls, and mentions no one else. (yes, Huckabee less now..)
You interpret that as "only these people have a decent chance of winning", or for a surprising amount of people "only these candidates are in the race", if I choose anyone else, I'll be wasting my vote.
This turns voting into a betting game. The force of the "majority" leads the sociable individual to take that as peer pressure, to believe in the same things and people.
At this point, it leads to a breakdown of what you need for democracy.
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Conspiracy theories cannot be rated as true or false. It isn't the normal type of theory that scientists come up with. Conspiracy theories can only be counted as "plausible but inconclusive" or "low plausibility".
And even if they do happen, conspiracy theories can be easily dismissed, as being a co-incidence because conspiracy theories don't have much solid evidence.
Finally, conspiracies can act like opinions - they are like vectors generated by logical thinking linking many correlative points of evidence together (like a line of best fit). Projecting it ahead, conspiracies point to an event, or a range of events that it predicts will happen in the future.
If these above are so, then what's the difference between a conspiracy theory and any other theory in politics or even science?