In national elections, the candidate already in office is most likely to win the election. In politics, people call this conventional viewpoint the "incumbency effect."
This term is generally accredited to Alan Abramowitz who wrote an influential article in 1975 titled, "Name Familiarity, Reputation and the Incumbency Effect in a Congressional Election." In that article, Abramowitz asserted that the electoral advantage of incumbency was most notable in the elections held for the U.S. House of Representatives. Elections take place in the House of Representatives every two years and each time, the incumbency advantage is easy to note. From 1976 to 2013, more than 90 percent of the political representatives in office won re-elections.