No midterm congressional elections in more than a dozen years have been as full of tension, drama and significance as the contests Americans will decide on Nov. 2.

With the war in Iraq winding down but the war in Afghanistan still hot, with the economy in disarray if not in distress, with the public impatient with politicians of both parties, and with an American president nearing the halfway mark of a difficult first term, voters will make decisions that will make a difference — changing the composition and perhaps the control of both houses of Congress, expressing a preliminary verdict on Barack Obama’s presidency, and setting in motion forces that will shape the 2012 election and American politics for the next decade.

Labor Day is the traditional start of the general-election campaign, and now that we have passed the starting gate, both the stakes and voter interest grow exponentially.

With so much in the balance, here is a viewers’ guide as your television is clogged with advertisements and your neighborhood is clogged with yard signs:

l Is the election a referendum, and if it is, on whom?

The Republicans would dearly like these elections to be a ballot on the Obama presidency, which they believe has been disastrous economically and dangerous diplomatically. The Democrats would like it to be a referendum on a different president entirely — one who won a health-care overhaul that has eluded presidents since Harry Truman, who reined in Wall Street, and who was willing to pump money into the economy to save Americans’ jobs and assure that a bad recession didn’t become a depression.

But it’s too late for that. The Democrats have won all those measures but are losing the public-relations war, and so a president who by their lights has been on the offensive is instead on the defensive. For that reason the Democrats are in the position of seeking to make the midterm elections a referendum on the Republicans, whom they portray as intransigent critics, masters of delay and opposition.

l Would a big setback in Congress, or even the loss of control of one or both houses, portend doom for Obama’s re-election?

The Republicans have been suggesting that the 2010 elections are no less a public statement on Barack Obama than the 1994 elections were a referendum on Bill Clinton.

But not so fast. The Democrats lost 54 House seats and eight Senate seats in 1994, relinquishing both houses of Capitol Hill for the first time in a half-century — but Clinton was re-elected two years later. (Recall also that two years into Ronald Reagan’s presidency, the Republicans lost 26 House seats, but Reagan won a second term in 1984.)

If President Obama was able to fall from Mount Olympus in the two years since his election, then who is to say that he cannot reclimb it, at least partially, in another two years’ time? The loss of both houses of Congress concentrated the mind of President Clinton a dozen years ago. He didn’t like it, but he profited from it.

l What is this election about?

That’s hard to answer because September’s speculation likely will not be November’s nostrum. Here’s what it won’t be about: race.

Though Mr. Obama’s race may be an undercurrent in 2010, the voters made a clear statement two years ago and there is no turning back. Americans may have fallen out of love with Obama, but they still love what they did in November 2008, which is to assert that they no longer will tolerate racial barriers to power.

If the economy continues to falter, the election will be about Team Obama’s stewardship of the nation’s counting house, with Republicans claiming that too much was spent to too little effect, that the government and the deficit have grown too large, and that the prerogatives of private industry have been jeopardized and the free market damaged.

But if the Dow finishes above 10,500 on the week before the election and some erosion in joblessness is evident, the Democrats will be positioned to say that they managed the nation out of one of the worst recessions in history.

Apart from the partisan battle, the struggle this fall might revolve around the question of what it means to be an Obama Democrat or to live in the Obama era. His critics have defined him. He has not responded with his own definition. We know less about Obama’s philosophy now than we did the week he won the Iowa caucuses.

l Who’s to blame?

This question begs another: For what?

For some voters the election might be about who is to blame for the lousy economy. For others, it is about the looming Iranian bomb. Or the difficulties in Afghanistan. Or American trade policies.

But this question, which is on everyone’s lips, is not really a question but a statement: Something’s wrong. Nobody feels good about anything. And nobody likes politicians.

The blame question might be the ultimate economic theme of this election, but that’s a shame because in some important ways the Obama economic plan is merely an extension of the George W. Bush economic plan.

But that won’t matter. Democrats are still blaming Bush for the economy circa 2008 (look for this to increase in volume and virulence this autumn), and the Republicans are blaming Obama for the economy circa 2010 (ditto). There’s something about an electorate that wants to blame a politician. And something about a politician that wants to blame another politician.

But it’s in all of our interests to have the election be about something besides blame. The winners, after all, will not be able to govern if they’re in office merely because the voters hated them less than the other guys. We deserve better than that, and we can do better than that.