So here are the three most likely basic scenarios for governing in 2005: • George Bush wins re-election, with continuing Republican majorities in both houses of Congress, probably with margins the same or a bit more generous than what we have now.

• John Kerry wins the White House, with continuing Republican majorities in both houses, with margins the same or a bit tighter than what we have now. [IMGCAP(1)]

• John Kerry wins the White House and the Democrats capture the Senate, either with a 50-50 or 51-49 effective margin, while Republicans retain the majority in the House.

Of course, these aren’t the only possibilities. Bush had negative coattails in 2000, and it is possible that could happen again, at least to the extent that Democrats could hit the trifecta in the Senate and gain a couple of seats to recapture a narrow majority. Bush could have everything turn his way, resulting in a landslide and real coattails, giving him a considerably more generous margin to work with in the Senate. There could be a real reaction against the status quo, resulting in a 1980-type election in which Kerry brings along enough Democrats to sweep to majorities in both houses. But frankly, the odds are long that any of these things will happen.

In the House elections, the band of possible outcomes is pretty narrow. This time, there may be 30 seats that are genuinely contestable between the parties, where no one would be stunned if either side won. In all of these seats, money will be sloshing around everywhere; few if any seats will change parties because of a wide disparity in spending. They are evenly divided now, meaning that for a party to gain 15 seats it would have to keep all its own tossups and win all the other side’s — the equivalent of tossing a coin 30 times and having it come up heads 30 times in a row. Of course, that analogy is imperfect; if there is a wind at the back of either party come November, it would be the equivalent of tossing a weighted coin (or a loaded die) 30 times. But given the parity in the electorate and the intensity of feeling on both sides, the chances of a political earthquake in House elections are slim. Democrats, with a good recruiting season and good fundraising, are feeling good about their prospects. Realistically, that could mean, if all goes really well, a gain of five seats but not a majority.

In the Senate, where each race has its own idiosyncratic elements, Democrats start at a serious disadvantage — 19 seats up to only 15 for the Republicans. They also must defend five open seats in Southern states, all carried by Bush in 2000, all ones where the incumbent Democrats would have been favored and all now in the highly contestable category, with Republicans holding an advantage in Georgia and South Carolina to start. Except for Georgia, Democrats have strong candidates in all these races and in several instances, Republicans have hotly contested primaries (something true for Democrats as well in Florida). [IMGCAP(2)]

But the past few weeks have provided very good news for Democrats in the Senate races as well. Strong candidates in Illinois, Colorado and Oklahoma, as well as the best possible candidate in Alaska, and a bitter Republican primary in Pennsylvania give the Dems serious targets of opportunity. Actually, given the number of volatile seats up this time in the Senate, we could see more of a net shift there than in the House, in either direction.

I am not writing this column to tread on Stuart Rothenberg’s expertly manicured turf, but to make another point. Take any of the three scenarios I started with and think about governing under it. They all have one conclusion in common: Governing will be a bitch. If Bush gets re-elected with comparable continuing GOP majorities in both houses, Democrats will be both crushed and bitter. If Bush tries to govern to the center, he will find a much more resentful and less cooperative minority party than he had in 2001 (when, remember, the education bill went through with broad bipartisan support). And he will find more difficulty pulling off the near-perfect party unity he has achieved with amazing regularity in the House during most of his first term. Conservatives are growing increasingly alarmed at deficits and the sometimes high-handed manner of the White House. Moderates may eventually tire of being the doormats used to get strongly conservative bills through the House as bargaining chips for conferences with the Senate.

Democrats in the Senate, whether numbering 49, 50 or even 44 or 45, will have every continuing reason to use filibusters and other delaying tactics to bollix up the works for the president — and he will no longer have Sen. Zell Miller (D-Ga.) to provide automatic votes for him or Sen. John Breaux (D-La.) to look for compromises. Finding the center will be even more elusive.

If John Kerry wins, Republicans in Congress will greet him the same way they greeted Bill Clinton in 1992 — all right, you’ve won, but don’t think the victory will mean anything. You’re on your own, find your votes on your own side. The prospects for Kerry actually repealing the top-end tax cuts and getting revenue to do a program for the uninsured or any other domestic initiative will be slim. Dealing with the mushrooming deficit problem will be an awful, rancorous process (it will be no better and maybe even worse in a Bush second term).

Both parties have largely vacated the political center in American politics, but little legislative progress can be made without moving to center ground. Will we find a center next year? Will the remaining moderates — people such as Sens. John McCain (R-Ariz.) , Joe Lieberman (D-Conn.), Evan Bayh (D-Ind.), Olympia Snowe (R-Maine), Chuck Hagel (R-Neb.), Mary Landrieu (D-La.), Dianne Feinstein (D-Calif.) and Susan Collins (R-Maine), perhaps joined by newcomers like Democrats Erskine Bowles (N.C.) and Chris John (La.) — be able to use their clout to force the president and both parties to move to their center ground? Will they be able to provide a different atmosphere that can allow other institutionalists such as Sens. Dick Lugar (R-Ind.), Pete Domenici (R-N.M.), Elizabeth Dole (R-N.C.), Lamar Alexander (R-Tenn.), Jeff Bingaman (R-N.M.) and Bill Nelson (D-Fla.) to join them? If not, we are in for a rocky and depressing road in Washington in the 109th Congress.

Norman Ornstein is a resident scholar at the American Enterprise Institute.