ASP.NET SignalR: to build the real time voting app, then broadcast the live result as votes come in.
D3.js: For data visualization. (Creating Pie chart to show the result)
React.js: To update UI in a very efficient manner for real time changes.
If you are new to React.js, I strongly recommend to read following tutorial:
React.js: Introduction and Hello World with ASP.NET MVC 5