WHEN Senate majority leader George Mitchell (D) of Maine announced that he was quitting Congress at the end of this year, official Washington was stunned. But on second thought, analysts said it wasn't so surprising.
``It's just a lousy job,'' notes Stephen Hess, a political analyst at the Brookings Institution. ``It just wears you down and grinds you out.''
Senator Mitchell joins seven other senators who are already bailing out at the end of this session. They include Sen. Donald Riegle (D) of Michigan, chairman of the Senate banking committee, Sen. John Danforth (R) of Missouri, an 18-year veteran, and Sen. Howard Metzenbaum (D) of Ohio, a champion of liberal causes.
Mitchell was a shoo-in for reelection in November. But he had quietly complained of his unrelenting, 18-hour days. He told one reporter: ``I work pretty much all the time.''
Considered one of the most effective majority leaders since Lyndon Johnson of Texas, Mitchell will be sorely missed by Capitol Hill Democrats.
The exclusive club of the Senate has lost some of its traditional comity in recent years. One analyst notes: ``Most of them don't even like each other.''
Mitchell's steady hand and persuasiveness helped guide key Clinton programs - including the 1994 budget and the North American Free Trade Agreement - though troubled waters.
The leader's unexpected decision has sent ripples in all directions.
In the Senate, it set off a scramble for the No. 1 post, a position vital to President Clinton's policies during the next two years. At least a half-dozen senators may seek the leader's job.
In the White House, it signals both opportunity and danger. Opportunity to install a ``new Democrat,'' in the Clinton mold, to push the president's agenda. But danger because Mitchell, while a more traditional liberal Democrat, may be tough to replace with someone as effective.
In Maine, it threw this year's Senate election wide open. Republicans are given a good chance to pick up the Mitchell seat, which until 1980 was occupied by former Democratic Sen. Edmund Muskie.
In Democratic circles, it added to growing apprehension that the party's once-secure, 56-to-44 margin in the Senate is at risk. GOP prospects for regaining a Senate majority in either 1994 or 1996 are climbing.
When he decided to quit, Mitchell joined not only seven other senators, but also 38 House members - an unusually high number - who have announced that this is their last year on Capitol Hill.
David Mason, an authority on Congress at the Heritage Foundation, says the rising exodus from the House and Senate is revealing, though not necessarily worrisome.
``It proves the country is still healthy, and that there is something more important than politics,'' he says. ``One of the problems with [some other countries'] authoritarian governments is that politics becomes the be-all and end-all. But in a healthy society, there are things more important than politics.''
In Mitchell's case, one thing more important than the Senate leadership might be an offer to become commissioner of baseball. It's a job that he says interests him. And the White House says he's on the list as a possible appointee to the Supreme Court - a job he says he would consider.
Yet Mr. Mason and others concede that the decisions by a growing number of lawmakers like Mitchell to leave indicates that not all is well in Congress.
Congress was once considered an acme of political achievement, a place where America's best and brightest sought to serve.
Yet in recent years, Congress has sunk steadily in public esteem. Public opinion polls show congressmen ranking lower in public regard than teachers, ministers, policemen, and a dozen other occupations.
Mason notes that as long ago as ancient Greece, Aristotle observed that in a democracy, politicians live for the praise of the masses. Today, they hear little praise. Critics like Ross Perot beat up relentlessly on Congress, and millions of voters concur. Qualities needed by lawmakers, including the ability to seek consensus, to negotiate, to compromise, get little public applause.
It was those qualities in Mitchell that were highly regarded by Clinton. The president told reporters:
``I didn't know George Mitchell very well when I became president, and therefore I didn't know what to expect. After the last 14 months, I can tell you that I think he is one of the finest, ablest people I have ever known in any kind of work.... We would not have had the success we had last year had it not been for his incredible persistence and patience and strength.''
Why is Mitchell leaving? ``This is the right time for me to consider other challenges and to give someone else a chance to serve,'' he said in a statement. ``I've made no final decision on the future. I'll consider other forms of public service and the private sector.''
Among several senators mentioned as possible successors to Mitchell's leadership post are:
* Tom Daschle of South Dakota. Although only in his second term, he is close to Mitchell and already considered a Senate insider.
* Wendell Ford of Kentucky. As majority whip, he is the No. 2 Senate Democrat.
* J. Bennett Johnston of Louisiana. Mitchell defeated him for majority leader in 1988, but he may try again.
* John D. Rockefeller IV of West Virginia. A staunch liberal and health-care champion, he would be firmly opposed by conservatives.
* John Breaux of Louisiana. The chief deputy whip, he seems to be on everyone's list of possible successors.
The next leader won't be chosen until after the November elections.