PRESIDENT REAGAN has been devoting great enthusiasm and energy to his tax reform bill. Meanwhile the budget, abandoned at the Capitol like an orphan in a basket, is making slow progress. The president has devoted much of his time this month to the tax bill and recruiting public support for it. His contributions to the budget have consisted mainly of sending down word that this or that change would be unacceptable. A conference committee has now spent two weeks working diligently to reconcile the House and Senate versions of the budget resolution, but so far hasn't much to show for its labors. It is always difficult to move a budget along in the absence of active participation by the president. This president's attention is elsewhere.

Viewed from the White House, the budget is an irritation and an embarrassment. The Reagan budget strategy of 1981 has not worked as advertised. Far from balancing the budget, the administration is still collecting less than $4 in revenues for every $5 that it spends, and the difference is currently $215 billion a year. Mr. Reagan has walked away from the whole subject and prefers to talk about tax reform, which draws warm applause. When he discusses it, Mr. Reagan tends to dwell on those features of his bill that cut people's taxes.

That brings you back to the budget. The congressional budget committees are struggling to reduce the deficit, amid hints and signals that the tax reform bill will increase it. The reform bill was not supposed to do that, but things seem to be slipping a little. The bill was intended to raise as much money as the present tax law does. But over the past week there has been a dribble of warnings from the Treasury itself that, when fully effective, the reform bill would raise 3 or 4 percent less than present law. In terms of this year it would amount to something over $12 billion, a substantial setback to the job that the two budget committees are trying to accomplish.

Tax reform is a more congenial topic, but the budget is more urgently important. Tax reform, if carried out skillfully, might improve the performance of the economy beginning around the end of this decade. The budget deficit directly affects the way the economy operates now, for it keeps interest rates higher than they would otherwise be, it keeps the dollar high, and it leaves American industry less competitive than it needs to be. Delay on the budget is dangerous. But the budget is bogged down in the conference committee in a long quarrel over defense spending and cost-of-living increases in Social Security -- central issues in American politics, from which Mr. Reagan has taken his distance.

Tax reform and the budget are competitors for political attention. Mr. Reagan is supporting the tax bill with all of his very considerable skill. But it is the budget that needs to have priority.