President Bush’s prime-time speech on Sunday changed the equation and the dynamic in Congress. Consider the issues on the agenda for the fall: [IMGCAP(1)]

• A prescription drug plan in which there are irreconcilable differences between the House and Senate that can probably be reconciled only by adding a healthy dollop of money onto the $400 billion price tag on the table.

• Thirteen appropriations bills, none yet passed through both houses and enacted into law, facing a budget deficit of $480 billion, according to the Congressional Budget Office, and a promise of even higher deficits given the stubborn unemployment numbers.

• A demand for higher troop levels in the Army, not accounted for in Defense appropriations or future projections. A demand for full funding for the “No Child Left Behind” initiative. A pledge by the president and Republican Congressional leaders to push to make the Bush tax cuts permanent, despite the agreement that resulted in the Senate enacting the tax cuts in the first place.

Now we can throw into the mix an $87 billion package for Iraq. How does Congress square the circle? How does it even begin to reconcile these broad policy pledges without abandoning some of them, curtailing future tax cuts, or allowing deficits to balloon to $550 billion or $600 billion as far as the eye can see?

All this suggests that the fall will be a remarkably difficult and contentious time. And that Bush, among his challenges, has to decide whether to shift his basic approach to Congress or continue it under a very different set of political conditions than he has faced in the past two years since Sept. 11, 2001.

Bush’s political standing is back around where it was pre-Sept. 11, with an approval rating in the low to mid-50s. His ratings on the economy are sharply lower, and his approval on Iraq is shaky. Even House Republicans are asking questions — a rarity — about the budgetary implications of Iraq. And just before Congress left for the August recess, even the House of Representatives gave the White House a couple of high-profile rebuffs.

When a president operates with sky-high approval and a reputation as a winner no matter what the odds, he has immense leverage with Members of Congress who fear his wrath and assume he will prevail. When he stumbles, the assumptions change, and the ability to exercise power attenuates.

So what has the basic Bush approach been on major issues? With rare exceptions, it has been to treat Congress as if the United States operated under a quasi-parliamentary system. The president has relied first and foremost on a House of Representatives as a House of Commons — whether as an offensive weapon, the impetus for major legislation or a defensive stopper, keeping dangerous bills that pass the Senate from being sent to his desk.

On major initiatives like the two big tax cuts and the Homeland Security Department, he has counted on the House giving him near-perfect party discipline so he can get bills passed on party-line votes that give him between 95 percent and 100 percent of what he asks for. Then he has tried to use the House bills to pressure (or bludgeon) the Senate into going along, trying to intimidate Democrats into avoiding filibusters and, if necessary, to find a handful of Democrats, as few as possible, to get bills through that are as close as he can get to his ideological predispositions. Then he tries to use the conference committee to move the bills closer yet to the House and move the conference reports to the Senate on a take-it-or-leave-it basis.

The defensive approach worked on patients’ rights, where the House produced a Bush-sponsored package that blocked the broadly bipartisan Senate bill from sweeping through to the president’s desk and enabled the GOP to kill the issue without looking like it had killed patients’ rights.

But the defensive strategy doesn’t apply when you are trying to enact — not kill — bills into law to show a robust domestic record as a presidential election approaches. And an offensive strategy is much harder to pull off when Senate Democrats are more hardened in their resolve to block strongly conservative initiatives — and when distrust of the president, in the aftermath of the 2002 elections and the defeat of Sen. Max Cleland (D-Ga.), makes hollow any promise, implicit or explicit, by the White House to treat better those Democrats who go along with presidential importuning.

Of course, these are not the only strategies the president has employed with Congress. On education in 2001, he employed a radically different broad centrist and bipartisan approach in both houses, negotiating from the get-go with liberal icons Sen. Edward Kennedy (D-Mass.) and Rep. George Miller (D-Calif.). On campaign reform, he employed a passive approach, leaving it up to both houses of Congress to work their wills while making it clear that he would sign whatever came to his desk. And on prescription drugs, he has used a hybrid of tax-cut strategy and education strategy, going broad bipartisan in the Senate while staying strictly and toughly partisan in the House. But his preference for draw-the-line-in-the-sand tough, parliamentary-style partisanship has become clear.

It is true that the president used this hard-nosed approach to achieve his first and biggest legislative victory, the big tax cut, when his political standing was shaky — his legitimacy under question soon after Bush v. Gore, facing the closest margins in Congress in 70 years, with negative coattails robbing him of momentum going into his first session in Congress. And it is true that the president fundamentally altered the country’s view of him with his performance in the weeks after Sept. 11. But it is unlikely that he can take the tough, partisan approach he used on tax cuts and apply it more broadly now. Democrats are more hardened and Republicans are more nervous than they were in early 2001, and 2004 looms large.

The dilemma for the president is that to get bills enacted, he needs bipartisan support — that means moving to the middle. To deal with hemorrhaging deficits while Iraq’s costs explode, he needs both bipartisan support and adjustment in the tax cuts. But moving to the middle will enrage his bedrock conservative base, and if past experience is any guide, that base will grow more assertive and less understanding as the president’s political standing declines. It will grow enraged if he pulls a Bush 41 and erases some tax cuts (read: support a tax increase).

Each move to the middle will also likely drive an even deeper wedge between the Republican House and the Republican Senate. And using the national and homeland security issues will be much harder for the president to do in 2004 than it was in 2002.

Can the White House find a new balance, or a new hybrid approach? Can it operate on an ad hoc basis, cobbling together strategies on the go for issues like prescription drugs, energy and Iraq? This promises to be a fascinating exercise in presidential/Congressional relations.