Since you’re wondering – wondering how likely a Democratic takeover of the House is right now – I’ll provide you the answer one of the shrewdest political analysts around might give. “Momentum,” says Jim Leyland, “is as good as your next day’s pitcher.”

Jim Leyland, of course, is the manager of the Detroit Tigers, and momentum is what the Democrats have in the wake of the Mark A. Foley scandal and the apparent remarkable Republican crackup of autumn 2006.

So the smart people are saying the Democrats have a lock on the House right now and are competitive in the Senate. Maybe they’re right. Top Republicans worry they could lose as many as 30 House seats, twice as many as the Democrats need to take back control of the House. The latest USA Today/Gallup Poll shows Democrats with a 23-point lead over Republicans, the largest Democratic lead in 28 years, but a misleading one because the contest for House control is conducted in 435 individual contests and not in one national referendum.

That said, this is a Democratic moment, which is a huge advantage for a party that has been out of power a dozen years and rudderless for perhaps even longer.

But it is only a moment. You will notice that the word momentum consists primarily of the word moment, which brings us back to the wisdom of Mr. Leyland, the magus of Michigan. Moreover, the Bush family, which faced a 17-point deficit in 1988, when George H.W. Bush was running against Gov. Michael S. Dukakis, almost certainly remembers that Democrats have peaked early before and might do so again.

But what if this big Democratic bulge is not a peak but a plateau? That would mean the end of the Republican revolution on Capitol Hill (put aside for the sake of argument some conservatives’ view, plausibly correct, that there hasn’t been anything very revolutionary about the Republican suzerainty on the Hill in the Jack Abramoff era). That also would mean the replacement of Republicans with Democrats in the speaker’s chair and at the heads of all the committees, including the very important Energy and Commerce (watch for hearings on energy prices and on profit gauging), Ways and Means (watch for an effort to roll back the Bush tax cuts), International Relations (watch for new initiatives to adjust U.S. policy toward North Korea and Iran) and Armed Services (you can expect to see Defense Secretary Donald H. Rumsfeld being questioned on Iraq every other Tuesday morning).

All that would follow a Democratic takeover of the House, but that would not be all, and that’s where it gets interesting.

Some cerebral Republicans actually are hoping for the Democrats to prevail, in part to teach a lesson to the conservatives who have lost their way and have become, as Winston Churchill once characterized Clement Atlee, sheep in sheep’s clothing, and in part to share some of the blame for the mess Washington and the country are in right now. If the Democrats remain on the outside, this thinking calculates, they’re free to take the offensive and criticize in 2008, when the stakes are far greater than they are in 2006. But give them power, and remind the voters two years hence that power means responsibility, and there might be a whole lot less criticizing going on from a group that might even find itself on the defensive.

But a Democratic takeover would embolden the forces who have been thirsty for power since their last sip of it in 1994. The Democrats have a pent-up demand for progressive programs, to be sure, but they also have a pent-up demand for revenge, which in politics is not usually a feast for the gods. That could ensure two more years of ever more bitter bickering between the parties as the Republicans, who took out their anger at 40 years of exclusion in the Democratic years, once again become the victims. Turnabout is fair play, but it is not necessarily productive play.

The key to a productive Democratic reign is to rein in the human impulse to pulverize those who have pulverized you, and also not to overreach.

The last time there was a big switch in power, the president whose party was repudiated (Bill Clinton) found himself in the mortifying, mouse-like position of arguing that the presidency was still relevant. That was a humiliating spectacle to endure and to witness, and it came when the nation was not at war. This time America is at war, and so the dynamic is different.

And the last time there was a big switch in power, the president whose party was repudiated found himself the target of all sorts of irritations, investigations and impeachment efforts, most of which he brought on himself, simply by acting like himself. You can fill in the rest of this paragraph and see what we might be facing, though those who yearn for the impeachment of President Bush should probably sober up. There isn’t enough time.

One more point to consider. The mastermind of the last party takeover was an alienating figure regarded as a genius, or maybe a mad genius, by his allies and as a madman, or maybe a dangerous madman, by his foes. The person playing the Newt Gingrich role in 2006 is Nancy Pelosi of California, the woman who would be speaker. She may be less of a genius to her friends and less of a madwoman to her rivals, but she has the alienation bit down pat.

All of this is to say two things. The first is that although the Democrats are in a commanding position, the election isn’t over yet. The second is that the crisis on Capitol Hill – the utter inability of members of the legislative branch to behave like adults, or to govern – isn’t a Republican problem or a Democratic problem but a congressional problem. The election may change things, but it is up to Congress to change itself, and until it does it won’t be a force for much in the country, except maybe ridicule.