Snip from a Salon opinion piece by Michael Lind, which argues that Obama's victory marks "the beginning of a new era in American history," and that such eras are sparked by technological change.
[W]hat causes these cycles of reform and backlash in American politics? I believe they are linked indirectly to stages of technological and economic development. Lincoln's Second American Republic marked a transition from an agrarian economy to one based on the technologies of the first industrial revolution -- coal-fired steam engines and railroads. Roosevelt's Third American Republic was built with the tools of the second industrial revolution -- electricity and internal combustion engines. It remains to be seen what energy sources -- nuclear? Solar? Clean coal? -- and what technologies -- nanotechnology? Photonics? Biotech-- will be the basis of the next American economy. (Note: I'm talking about the material, real-world manufacturing and utility economy, not the illusory "information economy" beloved of globalization enthusiasts in the 1990s, who pretended that deindustrialization by outsourcing was a higher state of industrialism.)
Naturally, the Americans alive during the founding of new American republics have other issues on their minds. The Civil War was fought over slavery, not steam engines, and the New Deal, for all of FDR's commitment to nationwide electrical power fed by hydroelectric dam projects, was animated by a vision of social justice. The broad outlines of technological and economic change merely provide the frame for the picture; the details depend on the groups that emerge victorious in political battles.
That is why it is too early to predict the outline of the Fourth American Republic. Its shape depends on the outcomes of the debates and struggles of the next generation. But it is possible to speculate about its life span. If the pattern of history holds, the Fourth Republic of the United States will last for roughly 72 years, from 2004 (or, if you like, 2008) to 2076. And if the pattern of the past holds, we will see a period of Hamiltonian centralization and reform between now and 2040, followed by an approximately 36-year long Jeffersonian backlash motivated by ideals of libertarianism and decentralization.