Create a survey with a Multiple Choice or Image Choice question where only a single answer choice is allowed, and label each answer choice with the name of a candidate.
Use the Email Invitation Collector since this ensures each respondent can only vote one time per email address, and you can keep track of who has or hasn't responded while keeping votes anonymous.
If you're using another collector type, change the collector options to allow only one response per voter and to make the survey anonymous.
Go to the Analyze Results section of the survey. As responses come in, you'll be able to see which candidate has the majority. Create a custom chart to customize the display of the results.
Share Instant Results. You can show respondents who's in the lead when they submit their vote using the Instant Results feature, or share the survey results so respondents can see live updates online.