The good news this Thanksgiving is that consensus government is beginning to work in Washington and it is likely to continue. Prospective successes for the policy managers now in office are more numerous and significant than generally realized. And those successes are likely to influence in a positive way the character of the next president and his government.

A budget agreement, reducing deficits by $76 billion in the next two years, has been signed and sealed. Congress will deliver on it, almost assuredly, because the consequences of reneging are too scary for anyone to contemplate.

Further assurance for the fragile world financial picture lies in the postponement of any action on the massive trade bill until some time next year. So laden is that measure with protectionist features and special-interest provisions that it can only benefit from delay.

Meantime, progress is being made on the military-political side of international affairs, at both the regional and the superpower levels. A slow, tentative and still precarious process of reconciliation and negotiation is under way in both Nicaragua and El Salvador.

Soviet leader Mikhail Gorbachev is on his way to Washington to sign an agreement that will remove intermediate-range nuclear missiles from Europe. He comes amid brightening prospects for progress on issues ranging from Afghanistan to strategic arms.

Hard-lining, head-bashing and demagogic provocation have lost their appeal. The vacancy on the Supreme Court apparently will be filled by Judge Anthony Kennedy, a sound conservative who is not so ideological in his approach as to raise the fear that he would capriciously reopen settled issues.

With Frank Carlucci succeeding Caspar Weinberger at the Pentagon, almost all the central positions in the Reagan administration are held by men of maturity and judgment who can work comfortably with those in Congress, in the departments and in foreign governments who may differ with them on particular policies. George Shultz, James Baker, Howard Baker, Alan Greenspan and Carlucci command respect individually and as a team. And the great exception, Attorney General Ed Meese, has at least temporarily seen his influence with the president eclipsed. Given Ronald Reagan's dependence on the quality of the counsel he receives, this constellation of advisers encourages confidence.

What is more heartening -- and surprising -- is the growing recognition that sensible and professional government is likely to continue beyond the next few months and into the next presidency. At this point, the likeliest prospects for the White House in both parties are figures of considerable experience and judgment.

They are not radicals, ideologues or outsiders. They are, instead, men who by instinct and training are prepared to deal with the tough policy constraints and the need for consensus that will confront the next occupant of the White House.

George Bush and Bob Dole, the two leading Republican contenders, are obviously men of this type. Bush is so much of an instinctive conciliator that the major challenge facing his candidacy is to articulate his basic priorities. Everything suggests that decision-making in a Bush administration would involve lots of consultation and negotiation. Voters still need to hear what, beyond his instinctive hospitality and good will, Bush would bring to the table.

Dole, a consummate insider, has moved from a background of sharp partisanship to a far greater degree of comfort and skill in dealing with political adversaries. He has demonstrated, both as majority and minority leader of the Senate, that he has the force of personality to make others step up to their responsibilities as well.

Most of the Democratic contenders have displayed their skills for briefer times or in smaller arenas -- which is one reason why they are underdogs for November at this stage. But Richard Gephardt and Albert Gore Jr. both are identified with successful legislative compromises on tricky issues. Michael Dukakis in Massachusetts both preaches and practices ''consensus'' government, and Bruce Babbitt learned some of the same tricks in Arizona, where opposition control of the legislature made it a greater challenge.

To be sure, there are candidates in both parties who tend to celebrate their role as the greater dissenters -- Paul Simon, Jack Kemp, Pete du Pont and Al Haig. And the two reverends -- Jesse Jackson and Pat Robertson -- are, by definition, outsiders running as critics of the political/governmental process rather than as practitioners.

But the odds remain good that the ''rediscovery of reasonableness'' that Washington is celebrating this Thanksgiving may be more than a passing phase. It could just be the next trend.