Congress and the President have gained a two-week respite in their efforts to trim down a mountain range of federal budgets looming ahead. The confusing Washington scene of recent days - a presidential veto, a brief theatrical shutdown of federal government, and a two-week stopgap spending pact in time to break for Thanksgiving recess - promises a repeat White House-Congress confrontation just prior to the capital's Christmas recess.
Politically, the President proved again he is in effective control of both houses of Congress. House Democrats, nominally in the majority, did not even try to override his veto. Democrats concede Mr. Reagan - despite a slackened public confidence in results from Reagan economic programs - can win a congressional test on any issue he defines as essential to his economic policies. ''He has all the cards,'' says Rep. Donald J. Pease (D) of Ohio.
''The Democrats, in many ways, would like the President to have a 'victory' because they really want this to be Reagan's budget,'' says one Washington budget expert. ''They don't want to be accused of messing it up.''
The unhappiest congressmen on Capitol Hill are the Republicans, also chastised - unfairly they protest - for ''budget busting'' actions when they thought they were following White House wishes, or waiting for the White House to make up its mind.
The tough tests ahead for the Reaganites actually lie more in resolving internal policy conflicts than in political skirmishes.
The White House can use the next two weeks to clarify what it really wants in the way of final fiscal '82 budget numbers. Democrats welcome the respite.
''The suspicion over here is that what the President is really pushing for is Congressman Pease, member of the Democratic whip team. ''He wants to substitute that for domestic spending, and he would go for current spending totals if he got that rearrangement of priorities.
''He claims, of course, we went only halfway toward meeting his halfway offer. But there are so many figures floating you can't tell who's right and who's wrong.''
Once the issues for the just-started fiscal-year budget are clarified, the political test should be decided quickly, likely in the President's favor.
But in January, the White House will have to launch into its planning for the fiscal 1983 and 1984 budgets. And it will have to decide between another deep gouging of federal spending and a tax hike.
''If they do an honest job of economic projections and carry out the budget numbers as they will have been passed up to that point, the administration is going to have 'frightening' deficit projects,'' says Robert W. Hartman, Brookings Institution economist.
''They're expected to come out with another big passle of spending cuts,'' Mr. Hartman says. ''Reagan has already warned everybody about that. The '83 budget is going to be as austere as the last one. The agencies are already reporting messages from the Office of Management and Budget, and it's 'disaster.' ''
More in doubt is what the administration will do on what it euphemistically calls the ''revenue enhancement'' side.
''A good case can be made for significant tax increases - not beginning immediately, because the economy will be weak in early '82,'' Hartman says. ''Natural gas deregulation and a tax on the price increase that will take place as a result of that, is a sensible way to get big revenue dollars. A gasoline tax is a good idea. But almost any tax increase will be a reversal of administration policy.''
The battle next year in Congress will likely be to fashion a compromise between smaller spending cuts and revenue hikes. ''That is difficult to see in an election year,'' Hartman observes. ''But that's the way it must come out, unless we get a stalemate, as we seem to be getting right now.''
The President must deliver three very important messages in coming weeks - the year-end economic message, the new budget message, and the State of the Union message.
''The numbers for the messages are being crunched right now,'' says Robert C. Brown, executive vice-president of the Tax Foundation.
''There is a legitimate concern among Reagan's people that nothing should happen on the Hill that will foreclose the kind of numbers and policies they have in mind,'' Mr. Brown says. ''That $1.5 billion or $2 billion difference in '82 spending might automatically be $4 billion or something much larger in the following budgets.''
Brown does not anticipate tax increases in 1982, an election year, although Republican leaders on the Hill will likely continue to push them. ''That puts all the burden on the budget cutting side,'' he says. ''They spared most of the big fish. Congress must face up to social security costs. That won't get done next year either.
''It's going to be tough. But the President's also pretty tough. He's in the driver's seat. If Congress were united, it would have overriden the veto.''
''We tend to look at the battle between the two institutions, the White House and Congress,'' Brown says. ''But the big battle is with the economy. The administration wants to be consistent in holding the spending line.''