A tea party upstart pulls an upset in Delaware so shocking that Republican Party leaders recoil from backing their new political star. Incumbents are toppled from coast to coast. The president with stars in his eyes falls to earth, along with his poll ratings. What’s to make of all this?

The country’s politics are in upheaval, and what has been happening all year in the nation’s civic life is remarkable — the shattering of a Democratic political movement that only a year ago looked like a formidable force for the new century, the growth of a grassroots insurgency of patriotism and protest that has moved from the fringe to center stage, and new uncertainties about the economy, tax policy and the 2012 election.

The result is a September surplus of unanswered questions and the most intriguing set of midterm congressional elections since 1994, when Bill Clinton was humbled and four decades of Democratic rule on Capitol Hill came to a stunning end — and perhaps even since 1938, when recession-ridden Democrats suffered a net loss of 72 seats and watched the New Deal magic come undone.

Here is a sampling of the questions that today’s political rebellion poses for American voters and for history:

• Is the Republican Party in the midst of a historic civil war?

The GOP has had wars before, often separated by 12 years’ time. In 1952, Old Guard conservatives struggled with the Eisenhower ascendancy. In 1964, Eastern moderates were forced to surrender to Western conservatives in the Barry Goldwater revolution that led to the Goldwater debacle at the polls. A dozen years later, in 1976 and 1980, resurgent conservatives led by Ronald Reagan battled Republican traditionalists like Gerald R. Ford and George H.W. Bush, eventually converting Bush.

It is in the nature of parties to undergo fights for their identity, and the Republicans aren’t alone.

The Al Smith Democrats mounted a challenge to the Franklin Roosevelt Democrats in the 1930s — a struggle between successive governors of New York, one of whom had, in a famous nomination speech, triumphantly described the other as the Happy Warrior. Anti-war Democrats led by Sen. Eugene McCarthy and Sen. Robert F. Kennedy rebelled against President Lyndon B. Johnson in 1968, providing an opening for Richard M. Nixon. Left-leaning Democrats assailed the party establishment at the convention that nominated George S. McGovern in 1972, changing the party for decades. Moderates, including Clinton, mounted a counterinsurgency after Walter F. Mondale and Michael S. Dukakis suffered disappointing losses in 1984 and 1988, respectively.

• How does today’s internal Republican fight differ from its predecessors?

It differs in a multitude of ways. It lacks discernible leaders, for example; there is no Robert Taft, Goldwater or Reagan this time. It is run by amateurs, not by political professionals. It has more in common with a recent GOP insurgency — the rise of the Christian Right — than with some of the earlier rebellions.

Like the Christian Right, the tea party movement consists largely of political outsiders, not office-holders. Like the Christian Right, the tea party insurgency represents a rejection of the broad cultural outlook of the ruling coalition.

The Republican Party has accommodated religious conservatives since 1988, which leads us to the next question:

• What is the likely historical role of the tea party?

The surprise victory of Christine O’Donnell in Delaware over a GOP stalwart, Rep. Mike Castle, has the unintended consequence of brightening rather than darkening the Democrats’ hope of retaining control of the Senate, making a historic sweep of both chambers on Capitol Hill almost impossible. Castle, a former governor of Delaware, likely would have produced a Republican pick-up by winning the seat once occupied by Vice President Joseph R. Biden Jr. Those prospects now have dwindled.

But in a larger context, the staying power of the tea party movement is perhaps the greatest unknown of the political season.

In some ways, the tea partiers resemble the Populists of the last decade of the 19th century. Eventually the Populists essentially merged with the Democrats, who nominated William Jennings Bryan in 1896. But the Democrats ended up co-opting the Populists, which allowed the Theodore Roosevelt Republicans to become the party of reform in the next decade.

With tea party victories in Alaska and Delaware still fresh and with tea on the breath of more than a dozen House, Senate and gubernatorial candidates (including Sen. Scott Brown, who won a special election to take the seat once held by Sen. Edward M. Kennedy of Massachusetts), Republican leaders worry that the tea party is a threat to take over their party. One midterm election season does not a permanent movement make. But a permanent movement is impossible without a midterm election triumph.

• Turning to the Democrats, can they recover in time?

If a week is a lifetime in politics, then seven weeks provide the Democrats with the seven lives they may need to survive. And the party’s prospects are better because of the gift they received this week in Delaware, a state that sometimes calls itself the Small Wonder.

Indeed, the GOP fissure was in full view by 10:45 p.m. Tuesday, when the tea party, reacting to the reluctance of national Republican figures to support O’Donnell, urged party leaders to “take a night off, get some sleep and reconsider their rash statements,” throwing in a dig at the National Republican Senatorial Committee by describing it as “just another big-government, Washington, D.C.-based organization that has contributed to the problems this country currently faces.”

A little more of this and the Democrats’ prospects may improve even more — but probably not enough to stave off a serious diminution of the party’s power in the Senate and perhaps a loss of control in the House.

• What does all this say about the 2012 election?

Here’s a surprise interpretation: The Democrats will be united behind a president whose approval rating, according to Tuesday’s Zogby International poll, now stands at 46 percent (slightly higher since the middle of last month) while the tea party rebellion continues to bedevil the Republicans.

No party likes to be divided going into a presidential election. Then again, no party likes to defend a president with an approval rating below 50 percent.