||The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. (January 2011)|
The coattail effect is the tendency for a popular political party leader to attract votes for other candidates of the same party in an election. For example, in the United States, the party of a victorious presidential candidate will often win many seats in Congress as well; these congressmen are voted into office “on the coattails” of the president.
This theory is prevalent at all levels of government. A popular statewide candidate for governor or senator can attract support for down ballot races of their party as well.
In New Zealand where a Mixed Member Proportional electoral system is in place, minor political parties can have a huge say over election results. There have been cases where party leaders from the major parties have endorsed politicians from minor parties. This is so that the minor party will be able to gain enough seats to get into parliament and therefore be able to pledge their support behind the major party which results in the major party being able to form a government with the assistance of the minor party. This has been an key issue in New Zealand politics particularly in the 2011 Election Campaign and in the Epsom electorate.
This also refers to the phenomenon that members of the U.S. Senate or House of Representatives are more likely to be voted for on a year of the presidential election than a midterm.
The "coattail effect" has also been used to derogatorily describe the effect of Group Representation Constituencies (GRCs) in Singapore, where candidates for Parliament run on a party slate of 3 to 6 candidates. This allows weak candidates to get elected "riding on the coattails" of strong candidates on their slate.
Presidential coattails is a term that refers to the ability of a Presidential candidate to bring out supporters who then vote for his party's candidates for other offices. In effect, the other candidates are said to ride on his coattails. In the 19th century voters cast their ballots by taking a ticket provided by a party worker and putting it in the ballot box. The party-column ballot listed all candidates of the party in a single column and allowed the voter to mark off the party box at the top, which encouraged straight-party voting and the coattails effect. Straight-party voting was the norm, and winners in Presidential elections often had long coattails. They almost always began their term with majorities in the House and Senate.
In modern times voting machines have replaced the party-column ballot with the office-column ballot: candidates are grouped by office rather than party. Often there is no way to cast a party-line vote, and each office must be voted on separately. The proportion of voters choosing House and Presidential candidates of different parties increased from 13 percent in 1952 to more than 40 percent in the elections of 1972, 1980, and 1988. Consequently, Presidential coattails have been virtually eliminated in most elections, and a number of Presidents—including Richard Nixon, Ronald Reagan, and George Bush —have begun their terms with one or both chambers of Congress controlled by the opposition party.
Presidents may suffer from a “reverse coattail” effect, in which more votes are cast for their party's candidates for the House or Senate than are cast for them. In 1976, for example, Jimmy Carter won the White House and obtained a total of 40,828,587 votes, but Democratic candidates for the House that year received 41,749,411 votes. In 1992 almost all Democrats elected to Congress won more votes in their congressional districts than the party's Presidential candidate, Bill Clinton; this may have had to do with the presence of a strong third-party presidential candidate, Ross Perot.
There is also the “negative coattail” effect, in which an controversial Presidential candidate may hurt candidates on the party's ticket running for lower offices. Barry Goldwater's poor showing in the Presidential election of 1964 led to the defeat of dozens of Republicans in the House of Representatives, leaving President Lyndon Johnson a large Democratic majority to pass his agenda.
Main article: Group Representation Constituency
Singapore introduced the GRC system in 1988, where candidates for Parliament run and are elected on a slate of 3 to 6 candidates in some constituencies, with a minimum of one minority candidate on each slate. The purported aim was to ensure minority representation in Parliament. However, it resulted in a "coattail effect" where unpopular and even unknown candidates are elected because they ran together with popular candidates (usually Ministers) on the same slate.
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