Government trifecta
A government trifecta is a political situation in which the same political party controls both the executive branch and the legislative branch in countries that have a legislative branch with two houses and have strict separation of powers. The term is primarily used in the United States. 

Most countries and all democracies have some degree of separation of powers into separate and independent branches of government consisting of an executive, a legislative, and a judicial branch, but the term government trifecta is only applied to countries in which the executive is not elected by the legislature. (In parliamentary systems, the executive [or part of it] is elected by the legislature and must have the support of the majority of the MPs but is otherwise separate and independent.)

Government trifectas are seen as beneficial by some and as undesirable by others. Those in favor argue that government trifectas are efficient and avoid gridlocks. Opponents argue that trifectas discourage policing of those in power by the opposition and that they do not limit spending and the expansion of undesirable laws. Opponents also argue that government trifectas do not tend to lead to compromise since one party can simply implement its goals unopposed. Consequently, the incumbent party may alter the structure of executive agencies to prepare for when it is bound to lose its incumbency. These alterations are performed to secure control over the agencies for when the party is no longer incumbent. Examples of these include political appointments that extend beyond the political cycle, contract or grant awards, and debt issuances.

The situation is common in developing nations but rare in developed ones. Early in the 20th century, for example, government trifectas were common in the United States, but they have become increasingly rare since the 1970s.

Government trifectas are contrasted by divided governments—a situation in which one party controls the executive branch while another party controls one or both houses of the legislative branch.

United States

The term is primarily used in the United States, where the federal government level consists of the president and the Congress with its two chambers (the House and the Senate). 

Because of the coattail effect, most newly elected presidents have a majority with them in both chambers of Congress. The six-year itch conversely means that the last two years of a two-term president rarely have trifectas. The most recent federal trifecta was held by the Republican Party from 2017 to 2019, and the last one before that was by the Democratic Party from 2009 to 2011.

State government trifectas
At the state level, a trifecta means that one party holds the governorship and both legislative houses. The sole exception is in Nebraska, where there is a unicameral legislature.

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