Why did Obama beat Romney?   Of the various explanations that have been offered – demographic changes, Romney’s shortcomings as a politician, a GOP funding bottleneck in June – the account I find most convincing is the old-fashioned one: the overall narrative process, driven by a naturally-occurring tipping mechanism.

Obama’s re-election was a further illustration of the zig-zag of politics. Because the world economy keeps growing, every twenty-five years or so, the US heads off in a different direction. It is never just one thing, of course. Everything a president does weighs in the balance.  But the public and its representatives have a way of picking out a few big themes almost as quickly as they are first sounded. And, reductive though the process may be, these motifs are the ones that that enter the history books.

A presidency, after all, is a story. The campaign beforehand may or may not offer clues to what comes next. The dominant themes often emerge only slowly from the welter of detail. But once they are inaugurated, presidents choose to tackle particular problems of their time, or not: sometimes, they merely keep an eye on them. They are judged on whether or not they are successful – first by the voters, then by history.

Almost always, since the beginning of the republic, these are problems that have arisen because of rapid economic growth (or, in the case of the Great Depression, the lack thereof), growth abroad as well as growth at home. Recognizing the direction of causation, from social and economic spheres to the political, is crucial to understanding the process.

Thus Theodore Roosevelt, who became president in 1901, after William McKinley was assassinated, governed until 1909, on various “progressive” reforms:  trust-besting, workers’ rights, conservation and other issues. After 1912, Woodrow Wilson resumed the pursuit of the progressive agenda until 1921, chiefly banking regulation (the creation of the Federal Reserve System). The articulation of America’s new position as a major power, and its entrance into World War I, dominated his second term.

After 1920, there was a pause in governmental innovation. Warren Harding, Calvin Coolidge and Herbert Hoover pursued what Harding famously called a “return to normalcy.”

Starting in 1933, Franklin Roosevelt pursued a New Deal that included compensatory government spending, new government regulation of financial markets, and the creation of a retirement security system. He was re-elected three times, the third and fourth terms coming largely because of his leadership during World War II. When Roosevelt died, in 1945, Harry Truman replaced him and, with the passage of the Full Employment Act in 1946, government for the first time assumed responsibility for moderating the business cycle.

After 1952, there was another pause.  Dwight Eisenhower kept the peace, sent troops to Little Rock to enforce Brown vs. Education, and built highways.

In 1960, John F. Kennedy campaigned on plans for extensive modernization of theUSeconomy in the contest with theSoviet Union. After he was assassinated, in 1963, Lyndon Johnson enlarged on Kennedy’s plans. He espoused a Great Society, whose policies emphasized civil rights, antipoverty programs, health care for the elderly – and a divisive war in Vietnam. .

Once again, there was a pause.  This time Richard Nixon gave the pause a name – détente. Gerald Ford and Jimmy Carter pursued it, too. The world economy continued to change – the oil embargo, the rise of Japan and the economies of Korea, Taiwan, Hong Kong and Singapore, the Iranian Revolution – but the US remained self-absorbed.

In 1980, Ronald Reagan was elected on the strength of a promise to restore order to an industrial economy that seemed to be spiraling out of control.  He supported Paul Volcker’s successful policies against inflation, endorsed the extensive restructuring of corporateAmerica, restored the Social Security system to actuarial balance, and, in the late stages of the contest with theSoviet Union, spent heavily on weapons systems. George H.W. Bush maintained Reagan’s policies after 1988 and saw the Cold War to a peaceful conclusion.

After 1992, there was another pause, though this time there was a difference.  The Democrats had declined, for the most part, to acknowledge the transformative nature if Reagan’s presidency. The Republicans now fiercely opposed Bill Clinton’s obstreperous initiatives, upping the ante to the point of impeaching Clinton for his venial sins.

The strategy only prolonged the pause. The eight-year presidency of George W. Bush, aside from its war-fighting and tax-cutting, extended the period of drift by the unusual expedient of offering something to almost everyone along the way – a failed assault on the Social Security System, the Medicare prescription drug benefit, the No Child Left Behind Act, the President’s Emergency Plan for Aids Relief.

In 2009, Obama returned the progressive tradition to the White House,  making the gradual restructuring of the health care system the centerpiece of his presidency and winding down an unwise and unjust war in Iraq and a botched intervention in Afghanistan.  (Compensatory government spending became a side issue in the end.

The alternating periods I have been describing in this Sunday shorthand often have been characterized as the cycles of American history. There have been many formulations including Ralph Waldo Emerson (“innovation is the salient energy; Conservatism the pause on the last movement”), Henry Adams: (“A period of twelve years measures the beat of the pendulum”); Albert Hirschman (shifting involvements between public and private purposes); and the two Arthur Schlesingers, father and son, as well.  (A good summary essay is contained in The Cycles of American History, by Schlesinger, Jr.

My favorite image, because it seems much less determinant, remains that of Robert Nozick, who, in The Examined Life, described “the zig-zag of politics.” He wrote:

The electorate I see as being in the following situation: Goals and programs that have been pursued for some time by the party in power, and the electorate comes to think that’s far enough, perhaps even too far.  It’s now time to right the balance, to include goals that have been, recently at least, neglected or given too low a priority, and it’s time to cut back on some of the newly instituted programs, to reform or curtail them.

The trick is to recognize that each new zig and zag involves a response to changing conditions in the world. Presidencies are stories about problems that arise in the world:  problems with foreign adversaries, of course; and problems associated with the rise of corporations and the advent of large cities, with banking panics, increasing life spans, poverty, inflation, globalization, the declining availability of health insurance, and, some day, climate change (just wait for the immigration problems that entails!). In each case reform has its day:  a strong stroke or two to cope, followed by a rest, like a feathered oar.

So what are Republican prospects going forward? They are better than you think, once the GOP resolves its differences with the would-be reformers in its ranks, the Tea Party and the supply-siders, and returns to the conservative task, defending the actual state of things, good and bad.  There will surely be another pause some years from now. But only after a good deal more political and social innovation has been tried and tested.