Though not currently enrolled in a party, he is known as a Democrat. But if he ran for the Senate, it would very likely be as a Republican or independent so he could avoid a costly primary.
As a candidate, Mr. Zuckerman would be following the path of a close friend and fellow media executive, Mayor Michael R. Bloomberg, who switched his party affiliation from Democratic to Republican to run for office. [More]
Professor Quigley? Your cue...