"Dark Blue" by Jack's Mannequin?

It's actually based on the 1969 film 'They Shoot Horses, Don't They?' (which is based on a novel of the same name). It's about a Depression-era dance marathon, which used to be a big fad; it was sort of the reality TV of its day. Like in the video, couples started dancing, then eventually dropped from exhaustion, and the marathon wasn't over until there was only one couple left standing. Some marathons have lasted days, even months, and are actually outlawed in several parts of the U.S.