Will the Levee Break?

By PAUL KRUGMAN

The conventional wisdom says that the Democrats will take control of the House of Representatives next month, but only by a small margin. I’ve been looking at the numbers, however, and I believe this conventional wisdom is almost all wrong.

Here’s what’s happening: a huge Democratic storm surge is heading toward a high Republican levee. It’s still possible that the surge won’t overtop the levee — that is, the Democrats could fail by a small margin to take control of Congress. But if the surge does go over the top, the flooding will almost surely reach well inland — that is, if the Democrats win, they’ll probably win big.

Let’s talk about Congressional arithmetic.

Unless the Bush administration is keeping Osama bin Laden in a freezer somewhere, a majority of Americans will vote Democratic this year. If Congressional seats were allocated in proportion to popular votes, a Democratic House would be a done deal. But they aren’t, and the way our electoral system works, combined with the way ethnic groups are distributed, still gives the Republicans some hope of holding on.

The key point is that African-Americans, who overwhelmingly vote Democratic, are highly concentrated in a few districts. This means that in close elections many Democratic votes are, as political analysts say, wasted — they simply add to huge majorities in a small number of districts, while the more widely spread Republican vote allows the G.O.P. to win by narrower margins in a larger number of districts.

My back-of-the-envelope calculations suggest that because of this “geographic gerrymander,” even a substantial turnaround in total Congressional votes — say, from the three-percentage-point Republican lead in 2004 to a five-point Democratic lead this year — would leave the House narrowly in Republican hands. It looks as if the Democrats need as much as a seven-point lead in the overall vote to take control.

No wonder, then, that until a few months ago many political analysts argued that the Republicans would control the House for the foreseeable future, because only a perfect political storm could overcome the G.O.P. structural advantage.

But what’s that howling sound? Every poll taken this month shows the Democrats with a double-digit lead in the generic ballot question, in which voters are asked which party they support in this election. The median Democratic lead is 14 points.

And here’s the thing: because there are many districts that the G.O.P. carried by only moderately large margins in recent elections, a large Democratic surge — one only a bit bigger than that needed to take the House at all — would sweep away many Republicans holding seats normally considered safe. If the actual vote is anything like what the polls now suggest, we’re talking about the Democrats holding a larger majority in the House than the Republicans have held at any point since their 1994 takeover.

So if the Democrats win, they’ll probably have a substantial majority. Whether they’ll be able to keep that majority is another question. But be prepared to wake up less than four weeks from now and learn that everything you’ve been told about American politics — liberalism is dead, whoever controls the South controls Washington, only Republicans know “the way to win” — is wrong. (Are we seeing the birth of a new New Deal coalition, in which the solid Northeast takes the place of the solid South?)

The storm may yet weaken. The Iowa Electronic Markets, in which people bet real money on election outcomes, still give Republicans a roughly 40 percent chance of keeping control of both houses of Congress. If that happens, will it mean that Republican control is permanent after all?

No. Bear in mind that the G.O.P. isn’t in trouble because of a string of bad luck. The problems that have caused Americans to turn on the party, from the disaster in Iraq to the botched response to Katrina, from the failed attempt to privatize Social Security to the sudden realization by many voters that the self-proclaimed champions of moral values are hypocrites, are deeply rooted in the whole nature of Republican governance. So even if this surge doesn’t overtop the levee, there will be another surge soon.

But the best guess is that the permanent Republican majority will end in a little over three weeks.