Paul Schreiber blogs about the tech behind the websites of presidential candidates. "So, you want to run a country. Can you hire someone who can run a website? ...Here's how the (declared) candidates' sites fare." There's a table comparing 4 candidates' sites based on HTTPS, URL permutations, IPv6, SSL rating, and other related qualities. Schreiber mentions that he will "update this as more candidates declare or sites change."
From the blog comments
HillaryClinton.com was using IIS (and no https) until Sunday morning, when they switched over.
No, it's because the more encryption there is, the harder it will be for the government to tell 'important' communication from 'unimportant' communication, thereby providing some cover for those that need encryption the most.