(To find out what 3-I means, read on)
A significant and growing literature on international relations (IR) argues that domestic politics is typically an important part of the explanation for states’ foreign policies. (…) I argue that what constitutes a “domestic-political” explanation of a state’s foreign policy choices has not been clearly elaborated. What counts as a domestic-political explanation is defined by opposition to systemic or structural explanations. But these may be specified in several different ways—I spell out two—each of which implies a different concept of domestic-political explanations. If a systemic IR theory pictures states as unitary, rational actors, then a domestic-political explanation is one in which domestic-political interactions in at least one state yield a suboptimal foreign policy relative to some normative standard. Or, if a systemic IR theory pictures states as unitary, rational actors and also requires that attributes of particular states not enter the explanation, then a domestic-political explanation is any one that involves state characteristics other than relative power. .
If I’m allowed some year-end kvetching: I’m amazed that theorists of international relations are just becoming aware of the link between domestic and foreign policy. It must have escaped their omnivorous attention that Julius Caesar conquered Gaul with more than a cold eye set on his position and power in Rome.
Be as it may, the sources of “domestic-political” factors, I would argue, may be endogenous or exogenous.
The power struggles in ancient Rome are an example of endogenous factors driving foreign policy.
Increasingly, exogenous factors are involved. A first step is the emergence of alliances among states. A further step would be the emergence of a common ideology facilitating alliances: the Roman Pope preached Crusades, and kingdoms marched toward Jerusalem. In a secular age, we had Comintern fomenting revolutions in distant countries.
The XXth century has seen a further development: foreign governments manipulating public opinion of another country to affect the latter’s foreign policy.
A glaring example is the “China Lobby,” which shaped the Asian policy in the US since the 1920s. Whether the China Lobby exists today is a futile question: it has engendered foreign policy thinking habits that have taken on a life on their own. The “domino theory” is one of the off-shoots.
I would recommend James BRADLEY’s The China mirage as a source of insights into ways of manipulating public opinion. The analysis of developments within the US makes sense, even though the profiles of some the participants are sometimes schematic (e.g. the author is starry-eyed concerning Mao Zedong.
Manipulation of public opinion – the book explains –best relies on the deadly “3-I”-combination: Ignorance and Idealism, buttressed by Interest. On such sturdy pillars, a narrative can be framed that obscures the view of the reality on the ground.
Here is the situation concerning China. Americans had no clue about China or the Chinese. They had never met any – having passed the Chinese Exclusion Act in 1882. Under the circumstances, any tall tale about the Chinese “wanting to become American” held sway, particularly if it is a self-affirming tale. It is a case of “Higgins disease:”
or, as the author points out: “Americans were not interested in what the Chinese were, but in what they might become.”
An ample flow of money greatly smoothes the process. Idealism is one of its best sources of money (with few strings attached and little oversight in its eventual use). The Soong family in China made its first money printing Bibles for the zealous missionaries eager to transform donations into texts. Having established itself, the Soong family became the interlocutor of choice – for a hefty consideration.
A PR-acquaintance once told me: “Say it loud and early.” That is how he went about framing a discussion to suit his aims. His advice is certainly worthwhile, but not infallible against 3-I. The scholarly Jesuit Matteo Ricci and his successors, who had done so much to bring Chinese thought to Europe, eventually lost out against the Franciscans and Dominicans, who knew very little of the country. Clement XI sided with the latter.
 James D. FEARON (1998): Domestic Politics, Foreign Policy, And Theories Of International Relations. Annual Review of Political Science Vol. 1: 289-313 (Volume publication date June 1998)
 “The Chiang-Chennault illusion that American airpower could have dramatic effects on the Asian mainland had long legs. McGeorge Bundy, Robert McNamara, and Henry Kissinger dropped more bombs on Asia than the U.S. military had worldwide in all of World War II, yet they lost.” (p. 361) The idea still survives now in Syria.
 James BRADLEY (2015): The China mirage. The hidden history of American disaster in Asia. Little Brown, & Co. New York.
 For generations, American hearts had been warmed by the missionary dream of a New China peopled by Americanized Christians. Then, beginning slowly in the early 1930s, a foreign-funded China Lobby sprouted in the United States and gained powerful adherents in the U.S. government, in the media, and in pulpits across the country. By 1941, nearly a decade of China Lobby propaganda had been pumped into American churches, homes, and heads, convincing the vast majority of Americans that a Christianized and Americanized New China would blossom as their best friend in Asia if the United States drove the Japanese military out of China. (p. 7)
 In 1973, as America withdrew from Vietnam in defeat, sixty-year-old Archimedes Patti asked the CIA if he could see the reports he had written from Hanoi about Ho Chi Minh in 1945 as an OSS officer. They were still tightly wrapped in Julia Child’s burlap, unread by the Wise Men. Patti observed: “In my opinion the Vietnam War was a great waste. There was no need for it to happen in the first place. At all. None whatsoever.… During all the years of the Vietnam War no one ever approached me to find out what had happened in 1945. In all the years that I spent in the Pentagon, in the Department of State and in the White House, never was I approached by anyone in authority.”
 “If the United States in 1945 had been able to… shed some of its illusions about China, to understand what was happening in that country, and to adopt a realistic policy in America’s own interests, Korea and Vietnam would probably never have happened.… We would not still be confronted with an unsolvable Taiwan problem.… And Mao’s China, having come to power in a different way and not thrust into isolation by a hostile West, might be quite a different place. —John Service, a China Hand who knew Mao quite well in Yan’an and was drummed out of the State Department under accusation of being soft on “Communism.”