When and why did Democrats and Republicans switched platforms??

The Republican and Democratic political parties in the US did not always agree with what they do today. The more liberal Democrats and the right-wing Republicans are represented by the same colour, blue and red, but they have different belief systems.
The Free Dictionary describes a system of government in which power is divided between a central authority and political units as a system of federalism. The transcontinental railroad, the state university system, and the settlement of the West by homesteaders were all funded by this. The Democrats were against those measures. The French newspaper Presse stated that the Republican Doctrine was the most Liberal in its goals but the most dictatorial in it's means.

The Civil War and Franklin Roosevelt.

The emergency banking act was signed by Franklin D Roosevelt.

The Civil Rights Act of 1866 was passed by the Republicans after the United States won the Civil War, but it did not end slavery. Democrats opposed the expansion of federal power.

It sounds like an alternate universe. Fast forward to 1936.

The New Deal helped President Franklin Roosevelt win reelection. The FDR Presidential Library and Museum described the Great Depression as a "severe, world-wide economic disintegration symbolized in the United States by the stock market crash on Black Thursday, October 24, 1929." These measures ensured Roosevelt's victory in the election against the Republican, who was against these exercises of federal power.

Between the 1860s and 1936, the Democratic party of small government became the party of big government, and the Republican party of big government became rhetorically committed to curtailing federal power.
Highly influential Democrat William Bryan.

How did this happen?

The transition to the turn of the 20th century was caused by a highly influential Democrat named William Jennings Bryan, who was best known for negotiating a number of peace treaties at the end of the First World War.
Republicans didn't immediately change their position of favoring limited government.
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Both parties promise an augmented federal government devoted in various ways to the cause of social justice for a couple of decades, according to an archive 2010 post for the Chronicles of Higher Education. Republican rhetoric gradually shifted towards the counterarguments. The party's small-government platform became popular in the 1930s because of its opposition to Roosevelt's New Deal.

Why did Bryan and other turn-of-the-century Democrats start advocating for big government?
Big government.

They were trying to win the west. The admission of new western states to the union in the post-Civil War era created a new voting bloc and both parties were vying for it.

There are 6 Civil War myths.

The Democrats used Republican federal expansions in the 1860s and 1870s to ingratiate themselves to western voters, and they found that the expansions were favorable to big businesses based in the northeast.
Both parties promised the general public some of the federal help that had previously gone to the business sector. Democrats stuck with their stance of favoring federal funded social programs and benefits while Republicans began to advocate for hands-off government.

The loyalties of the parties did not really change from a business perspective. "Although the rhetoric and policies of the parties do switch places, their core supporters don't," he wrote, "which is to say, the Republicans remain, throughout, the party of bigger businesses."

Businesses needed things that a bigger government could provide, such as infrastructure development, a currency and tariffs. The government became better for business once these things were in place.
Live Science published the original article. The article was updated in December of 2021.