Republican Thomas E. Dewey was elected in 1948, predictably breaking Democratic hegemony that had lasted since 1933. The leader of the Liberal wing of the Republican party, Dewey an internationalist and more socially liberal than some economically liberal and politically internationalist Republicans (as shown in the debate against Stassen, the Liberal Republican and UN involved wunderkind who recommended banning the Communist Party, to which Dewey won the debate in the eyes of most by replying famous "you can't shoot an idea with a gun"). The 1946 elections left the Republicans in complete control of the government, with majorities in both the House and the Senate along with Dewey in the White House. However Dewey and the Liberal wing were intent on keeping most of the New Deal programs. The one significant New Deal institution they did not maintain were the war time wage increases mandated by the Roosevelt government and kept by Truman. Most speculated at the time that with a Republican Congress not even Truman would have been able to justify keeping those war time controls on wages (this is the point of divergence: in our history the wage increases were responsible for the immediacy of the middleclass boom, whereas with only other components such as the GI Bill's subsidies for higher education the creation of a large middleclass will be postponed and altered).
In those post-war conditions, with internationalist Republicans and a President determined to counter Soviet power by winning hearts and minds in charge of the country; Henry A. Wallace, former Vice President under FDR (between Garner and Truman), began a movement that would change America.
Wallace had been Secretary of Agriculture from 1933 to 1940, Vice President of the United States from 1941 to 1945, and Secretary of Commerce from 1946 until Dewey assumed office and replaced him in order to fulfill promises made to other Republicans for their support of the Liberal Wing.
Wallace was considered naively pro-Soviet, even by American socialists like Norman Thomas, and because those who wanted to appear moderate by nominating a non-Socialist like Wallace and those who wanted to avoid being associated with the Soviet Union through Wallace couldn't work together the proposed 1948 Progressive Party presidential campaign had never materialized (another POD, in our history Wallace did run as the Progressive candidate but recieved no electoral votes unlike Dixiecrat Strom Thurmond, and was ridiculed for his mystical beliefs in the press in the process). However, due to his work as Secretary of Agriculture, he was considered a hero to many American farmers and was, as his securing of the Commerce position after being dropped from th Democratic ticket shows, in some ways a savvy Washington insider despite his unflattering associations with Communists and the guru Nicholas Roerich.
It was from this situation in 1948 that Wallace founded one of the most influential political pressure groups and lobbying organizations in American history; the Salem Institute. With huge initial support from farmers worried that the Republicans would take away their subsidies, Wallace used his contacts in the magazine world from his early professions as an editor to create a mass media machine to promote and support farmer's issues and agricultural science all over America. By advocating scientific and industrialized farming methods impressed into him by the Soviet Union, without any of the accompanying collectivization (with more time spent among farmers as in his youth making him realize how unpopular the idea would be), he managed to secure major donations to the Institute from the manufacturers of agricultural equipment. The advances made by Institute initiatives in agricultural science created a similar arrangement with the food industry and the transportation interests that profited primarily from the transit of food across America. This made the apolitical Institute, which advocated farmer's issues and agricultural science without extended ideological trappings, a powerful thinktank and lobbying group.
Wallace's reconciliation with the anti-Communist Progressives and socialists would occur later in the 50's when the Soviet Union betrayed the United Nations, in which the Dewey administration had invested much support and effort, over the spread of Communism in Korea. Wallace and the socialists agreed, with the majority of Americans, that the Communists were not acting in good faith; compared to the United States' own commitment to international democracy as shown by recognizing the independence of Vietnam in 48 and using UN pressure to get the French to leave the former colony. This not only put industrial progressives and socialists in the corner of Wallace's agrarian Institute but also synchronized Wallace's opinions with that of most Americans for the first time in his politically active life.
From that point until his death in the 1960's, Wallace would use the much expanded Institute as a platform for his now popular political ideas; with Institute-backed newspapers and periodicals like the New Republic supporting the worldwide spread of democracy against colonial and communist dictatorships, as well as branching out from agricultural to labor issues as well. This segued into the Civil Rights movement crystalizing under the Institute's wing; someone who had great credibility speaking out against racial violence as Vice President, it was part of Wallace's final legacy to combine not only the farmer and labor movements of Cold War America but also the movement against racial prejudice and against colonialism (Western or Communist) in the third world.
Of course, this expansion of the Institute's umbrella of political, economic, and media organizations was only one half of Wallace's final legacy before his death.
Post-war America was very prosperous, but it was still a blue collar nation of industrial workers and farmers. The middleclass would not really begin to form until the later 1950's due to educated white collar workers thanks to the GI BIll's educational provisions, and it would develop slowly. The possibility of expansive suburbs and white flight never materialized; most Americans in the post-war era either lived on farms and small towns or in the cities. With the increasing number of people, population pressure became a problem and it seemed that industrial production to match the need for employment and the need to spread out the population would have to encroach into the realm of the farmer. With a massive outcry against the perceived attack on America's farmland in the name of "dark satanic mills" (to quote the English Romantic William Blake), the US government and private sector largely adopted scientific planning measures proposed by groups such as Wallace's Salem Institute and the Technocratic Foundation. Planned communities and industrial parks, meant to maximize space in the cities and minimize impact on the land in rural areas, were a success; but they did little to change growing public resentment of urban life on one hand and the desire to move away from their home town and embrace their pioneering spirit on another.
The solution to this public discontentment was Wallace's final and most unlikely legacy.
In the final years of his life, his personal sense of mysticism resurfaced (never as brutally crushed in this world as in ours due to him not running for president in 1948 and thus his connection to the guru Roerich never being publicly ridiculed) and despite the cries from his staff nothing could stop him from letting it heavily color Institute publications and talking points. In this way before his death he spread his strongly felt sense of Naturalism (this world's term for something like a cross between environmentalism and the New Age movement) to many in his nationwide, and in fact international, movement. Naturalism would be considered by later writers examining the period to be something many Americans embraced to find their own reason for being in the previously sterile planned communities of the Post-War Era.
In the 1980's, twenty years after his death, Henry A. Wallace's movement would go from one institute and then a vast but loose collection of groups to being unified into a major American political party, with it's own affiliated parties in other nations.