Most — if not all — candidates have a Facebook page. Most — if not all — candidates have a Twitter feed.
But, to my knowledge, Chris Murphy is the only candidate to have a page on Google+, though he hasn't been posting very much to it.
If I'm wrong, and you know of another candidate using Google+, let me know.
Analyst Paul Allen said that there will be 400 million people on the social networking site by the end of 2012, but if that will held Murphy in his bid for the U.S. Senate remains to be seen.
(Oh, and by the way, I have a Google+ page, too.)