In the United States, the meaning of the term has changed dramatically over the last 60 years. Before the American National Election Study (described in Angus Campbell et al., in The American Voter) began in 1952, an individual's partisan tendencies were typically determined from their voting behavior. Since then, "partisan" has come to refer to an individual with a psychological identification with one or the other of the major parties.
American politicians have generally been identified with a party. Many local elections in the U.S. (as for mayor) are "nonpartisan." A candidate may have a party affiliation but it is not listed on the ballot. Independents occasionally appear in major contests but rarely win. At the presidential level the best vote getters were Ross Perot in 1992 and 1996, and John B. Anderson in 1980. In 2016 Bernie Sanders, an independent Senator from Vermont who caucused with the Democratic Party for years, entered the Democratic Party primaries and made a strong second-place finish, and left the party after the 2016 Democratic National Convention.
President Dwight D. Eisenhower was nonpartisan until 1952, when he joined the Republican Party and was elected president. More than any modern president he had a nonpartisan image in domestic affairs. According to David A. Crockett, "Much of Eisenhower's nonpartisan image was genuine, for he found Truman's campaigning distasteful and inappropriate, and he disliked the partisan aspects of campaigning." With little interest in routine partisanship, Eisenhower left much of the building and sustaining of the Republican Party to his vice president, Richard Nixon. "With few formal duties, Nixon threw himself into state and local politics, making hundreds of speeches across the land. With Eisenhower uninvolved in party building, Nixon became the de facto national GOP leader."
Eisenhower paid close personal attention to foreign and military affairs. However in domestic policy, his avoidance of partisanship meant that he did not interfere with the conservative policies of Senate leader Robert Taft. The Democrats regained control of both houses of Congress of 1954. Eisenhower's largely nonpartisan stance allowed him to work smoothly with the Democratic leaders Speaker Sam Rayburn in the House, and Majority Leader Lyndon Johnson in the Senate. Jean Smith says that:
The dictionary definition of partisan at Wiktionary