I thought, hmm. I wonder if we can figure out who his parents are? So, I looked him up in wikipedia, where I learned that R. had given me the wrong first name, also that the gentleman was born in 1936 in East Orange, NJ and graduated high school in Milford, CT. Also, he's a Jr. Hmmmm.
Off to ancestry.com, where typing in 1936, the name without jr, and the birthplace of NJ popped up a 1940 census record with him, his younger brother, and his parents in Milford. Looks good. Track up his dad to his grandfather, and then continue along (helpful DAR application information), where I topped out in the mid-19th century (unfortunate situation with some kids orphaned when both their parents died -- very sad). A little poking at ancestry's search engine further and I identified the parents and from there, it was quick work to place the result in my massive tree of other people with the same last name (we spent a lot of time on these guys tracing everyone living on this one particular street -- it made sense at the time ...).
Anyway. Long story short, the shared ancestor is just above the couple that died in the tragic runaway horses/broken harness incident coming home from church that didn't kill the grandchild in the carriage, thus making my mother-in-law the fourth cousin of the politician that I predicted we would discover her to be.
Mmmm, domain knowledge. *happy dance* Elapsed time: half an hour.