Old-school, you would right-click the page, read through the entire source, and track back any .js links (which are likely going to be minified).
But, to answer your question, yup -- you can use the element inspector in your dev tools of choice. I'm speaking from Chrome, because you referred to it and because I actually really like it. In the element inspector, you'll see the element itself to the left side, and three tabs listed on the right: 'styles', 'computed', and 'event listeners'. In the case of your electoral map, click into the Event listeners tab and check out 'mouseover' -- it tells you where the event is handled. clicking on the .js file given will open it in the 'sources' tab of the dev tools. Be warned, it's been minified to both save space and to confuse reverse-engineering a bit.