In the United States the term "deep state" is used within political science to describe influential decision making bodies within government that are relatively permanent whose policies and long-term plans are unaffected by changing administrations. The term is often used in a critical sense vis-à-vis the general electorate to refer to the lack of influence popular democracy has on these institutions and the decisions they make. The term was originally coined in a somewhat pejorative sense to refer to similar relatively invisible state apparatus in Turkey and post-Soviet Russia. With respect to the United States, the concept has been discussed in numerous published works by Marc Ambinder, David W. Brown, Peter Dale Scott, Mike Lofgren, Kevin Shipp and Michael Wolff.
While definitions vary, the term gained popularity among various groups, primarily supporters of Donald Trump and conspiracy theorists, during the 2016 U.S. presidential election, in opposition to establishment Republican and Democratic candidates. Since Trump's inauguration, the term has been used by commentators who argue that a deep state, involving the FBI, CIA, NSA, former President Barack Obama, and/or Hillary Clinton, is aiming to delegitimize the Trump presidency and thwart its policy goals.
The term deep state was defined in 2014 by Mike Lofgren, a former Republican U.S. congressional aide, as "a hybrid association of elements of government and parts of top-level finance and industry that is effectively able to govern the United States without reference to the consent of the governed as expressed through the formal political process."
In The Concealment of the State, Professor Jason Royce Lindsey argues that even without a conspiratorial agenda, the term deep state is useful for understanding aspects of the national security establishment in developed countries, with emphasis on the United States. Lindsey writes that the deep state draws power from the national security and intelligence communities, a realm where secrecy is a source of power.Alfred W. McCoy states that the increase in the power of the U.S. intelligence community since the September 11 attacks "has built a fourth branch of the U.S. government" that is "in many ways autonomous from the executive, and increasingly so."
In the journal Foreign Affairs, UCLA Law professor Jon D. Michaels discusses Trump and the deep state, and argues that the concept's relevance is quite limited in the United States. He states that it is a more useful perspective in the study of developing countries such as Egypt, Pakistan and Turkey, "where shadowy elites in the military and government ministries have been known to countermand or simply defy democratic directives."
The term has been appropriated by Breitbart News and other conservative and right-wing news outlets, where supporters of the Trump Administration have used it to support a variety of conspiracy theories. It has been dismissed by authors for The New York Times and The Observer.University of Miami Professor Joseph Uscinski says, "The concept has always been very popular among conspiracy theorists, whether they call it a deep state or something else."
According to whistleblower Edward Snowden, "the deep state is not just the intelligence agencies, it is really a way of referring to the career bureaucracy of government. These are officials who sit in powerful positions, who don't leave when presidents do, who watch presidents come and go...they influence policy, they influence presidents."
The term "deep state" has been associated with the "military-industrial complex" by several of the authors on the subject. Potential risks from the military-industrial complex were raised in President Dwight D. Eisenhower's 1961 farewell address: "In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military-industrial complex. The potential for the disastrous rise of misplaced power exists and will persist." Mike Lofgren has claimed the military-industrial complex is the private part of the deep state. However, Marc Ambinder has suggested that a myth about the "deep state" is that it functions as one entity; rather, that parts of the "deep state" are "often at odds with one another."
President Barack Obama's alleged lack of success of his campaign promises relating to the Afghanistan war and civil liberties has been attributed by Tufts University professor Michael J. Glennon to what he calls the "double government"; the defense and national security network. Mike Lofgren felt Obama was pushed into the Afghanistan "surge" in 2009. Another major campaign promise Obama made was the closure of Guantanamo Bay Prison Camp, which he was unable to accomplish. This has been attributed indirectly to the influence of a deep state. 
Donald Trump supporters use the term to refer to their allegations that intelligence officers and executive branch officials guide policy through leaking or other internal means. According to a July 2017 report by the United States Senate Committee on Homeland Security and Governmental Affairs, "the Trump administration was being hit by national security leaks 'on a nearly daily basis' and at a far higher rate than its predecessors encountered".
The term has also been used in comments on the "deep state"-like influence wielded by career military officers such as HR McMaster, John Kelly and James Mattis in the Trump administration. This sub-presidential peer group has been sardonically described as an "axis of adults" (a reference to the "axis of evil" and Trump's supposed infantilism).
Following Trump's provision of "total authorization" to the military and the subsequent use of a MOAB in Afghanistan, the anthropologist C August Elliott described the rise of a "shallow state" in the US: "an America where public servants now function as tugboats guiding the President's very leaky ship through the shallows, away from a potential shipwreck."
Donald Trump and Steve Bannon, his former chief strategist, have both made allegations about a deep state which they believe is interfering with the president's agenda. In 2018, describing the deep state as an "entrenched bureaucracy," Trump accused the United States Department of Justice "of being part of the 'deep state'" in a statement advocating the prosecution of Huma Abedin. Some Trump allies and right-wing media outlets have alleged that former President Barack Obama is coordinating a deep state resistance to Trump. While the belief in a deep state is popular among Trump supporters, critics maintain that it has no basis in reality, arguing that the sources of the leaks frustrating the Trump administration lack the organizational depth of deep states in other countries, and that use of the term in the U.S. could undermine confidence in vital institutions and be used to justify suppressing dissent.
According to a poll of Americans in April 2017, about half (48%) thought there was a "deep state", "meaning military, intelligence and government officials who try to secretly manipulate government." Of those who thought that, more than half (58%) said it was a major problem (net of 28% surveyed). A March 2018 poll found most respondents (63%) were unfamiliar with the term "deep state", but a majority believe that a deep state likely exists in the United States when described as "a group of unelected government and military officials who secretly manipulate or direct national policy". Three-fourths (74%) of the respondents say that they believe this type of group definitely or probably exists in the federal government.