Don't allow users to see how others have voted until voting or giving up the right to vote.

[brinerustle]

In close races, late voters can easily affect the outcome by lying about their preferences to exclude a date for which they may be available. Early voters do not have this advantage, their best strategy is to be honest. People know this, which leads to procrastination in high-stakes polls, which is counterproductive when using a poll to schedule.
Expected behavior: When you open a poll, people's responses should be greyed out. You should see the names of those who have voted (so you can see if you have already voted if you can't remember) but only when you submit your responses should the results appear. There should also be a button which says Show Results. This should lead to a popup with two choices, perhaps I don't want to vote and oops, let me vote first, either showing results and removing the option to vote, or returning to the polling screen.