Ronald Reagan has done a skillful job of holding the initiative on the fiscal policy issue in his first four weeks as president, but now the game gets much tougher. Other kinds of political skills -- including those of hand-to-hand combat -- will be required, and the cohesiveness of the new administration will be tested in ways that will show how strong its dicipline really is.

In the first phase of the operation, Reagan has played the outside man effectively, while budget director David Stockman has done the heavy work on the inside. The combination has been impressive.

During this phase, Reagan has accomplished one major objective. He has gained legitimacy across the political spectrum for the particular view of economic policy he enunciated in the campaign. It is a view that asserts that a specific combination of tax cuts and budget reductions holds the key to reducing inflation and spurring economic growth.

Reagan began that process in his inaugural speech and has continued it in his television address on the economy two weeks ago and in the state of the economy address tonight. He has reiterated the same theme in meetings with congressional leaders, governors, mayors and the representatives of key constituency and interest groups that filled his calendar during his first weeks in the White House.

While participants in those meetings generally say that the president steered the conversation away from substantive debate, the due difference with which they couched their comments after seeing Reagan has created an impressions of general consensus around his broad economic strategy. That is no small accomplishment. Despite the sweeping victory Reagan won last November in a campaign in which he was quite explicit about his economic views, polls show the public to be fairly skeptical about key principles of Reaganomics. The voters have been telling the pollsters that they would give much higher priority to a balanced budget than to tax reductions, but Reagan is promising a balanced budget in fiscal 1983 at the earliest. By that time, he is proposing to cut everyone's tax rates by 30 percent.

The polls also suggest that the public is skeptical that Reagan will have much more luck than past presidents in reducing inflation by the method he is proposing. Nonetheless, his own speeches and meetings have created a sense that it would be wrong to deny him a chance to try.

Whether that predisposition to accomodation -- call it a "honeymoon" -- lasts is problematical. Across the country, newspapers, including such conservative stalwarts as the Dallas Morning News and the Chicago Tribune, have been spelling out to their readers the costs in popular local projects from Reagan's proposed cutbacks.

In Washington, preliminary meetings to thwart the Reagan plan are already being held. Logrolling was not made illegal by the last election, and representatives of constituencies whose pet programs are under threat are talking earnestly with each other about how to limit the damage.

None of this comes as a surprise to the people in the White House. A major political campaign involving substantial private and public resources is being prepared to "sell" the Reagan plan to Congress, even against the din of expected criticism and intense interest-group pressure. e

But in the weeks ahead, the administration and the president will be tested.

Stockman has had an advantage in gaining acquiescence to the budget cuts from the fact that few of the Cabinet members were well staffed to defend their own programs. But they will be better briefed by their own bureaucracies when the congressional hearings begin, and it will be interesting to see how enthusiastic all of them are about the reduction of their own empires.

Stockman himself has left a few bruised feelings in important places as he has hammered through his package of cutbacks. While the top-ranked professionals in the budget offices are pleased to see the chief displaying his clout with the president, they would be more pleased had the 34-year-old whiz kid been a shade less assertive in his commands and a shade more receptive to their thoughts. The private doubts of some budget professionals about the practicality of the Stockman reductions are not likely to remain private forever.

Washington, in short, is about to move out of the area of rhetoric and into the trenches. And we will see how Reagan and his folks do in trench warfare. t