"You have sat here too long for any good you have been doing. Depart, I say, and let us have done with you. In the name of God, go."

The famous words addressed by Cromwell to the Long Parliament -- reiterated the day before Chamberlain gave way to Churchill -- now strike home in Washington. In the wake of the Billy affair, millions of Democratic voters, and a not inconsiderable part of the Democratic Congress, would like to dump Jimmy Carter.

Edward Kennedy and John Anderson would both probably make it easy by effacing themselves. But senior Democrats, whose position is crucial, are standing pat.

The general condition of the country lies at the root of this discontent. By any account, the United States faces extremely hard challenges. It has to turn around recession without stimulating a new bout of inflation. It has to move toward energy independence without aborting recovery. It has to siphon off resources for stronger defenses without destroying arms control negotiations and cohesion among our allies.

Many normally Democratic voters would like, as a protest against the leadership that put the country where it is, to vote Republican this year. But Ronald Reagan has not surfaced any credible map for escape from the present difficulties. His inexperience suggests he would be ineffective in office -- "the Republican Carter." So many persons prepared to embrace his party draw back before his candidacy.

John Anderson offers on both domestic and foreign affairs some good points, but not a program. He is so much a loner there seems small chance he could be elected. Signs from the Anderson camp hinted willingness to withdraw in the event developments winkled Carter out of the running.

As the governing party, the Democrats would normally be expected to put forth a candidate equal to the occasion. But Carter clearly doesn't fit the bill. Not only are his policies directly responsible for the national distress but he shows no capacity for change.

For example, in an interview with The New York Times Magazine on goals for a second term, Carter placed emphasis on revitalizing American industry. In duscusing that goal, he talked of a "partnership between government and business." But only provided it was "within the bounds of propriety."

In other words, the president still sees something illcit in good relations with the business community. Experience has taught him nothing, nor can it be believed that a second term, free of constituency pressures connected with reelection, would be different. As much as ever, Carter is in the grip of the moralistic, small-town populist values that have so characterized his first term.

The Billy affair, in these conditions, has been seized upon by many Democrats as an occasion for unloading the president at the convention in New York. The 40 House members who have expressed an interest in forcing the president out comprised a typical expression o that sentiment.

They are not Kennedy supporters, and they believe -- probably rightly -- that Kennedy would withdraw if Carter also excused himself. But neither are they typical centrist Democrats. They tend to come from what were once Republican districts. They can expect to lose their seats in a Republican tidal wave this year.

The revolt of the 40 can yield results only if it finds support among senior Democrats. Persons like Senate Majority Leader Robert Byrd, Speaker of the House Tip O'Neill and Lane Kirkland, the president of the AFL-CIO, would have to be part of any successful drive. But a continuing check on senior Democrats over the months shows little change in outlook.

They think, first, that the election is still winnable with Carter at the head of the ticket. They further believe that dislodging Carter would be very tough. They see in the president the personification of tenacity. They are not sure they could shake Carter or his delegates even if they laid all their prestige on the line. They believe that if they did force a withdrawal, the circumstances would be brutal and bound to leave blood all over the floor.

Finally, they think that with Carter out, the Democrats would probably lose the election anyway. Of particular concern on that score is that the South, miffed at the dumping of a native son, would turn against the Democratic Party.

The prospect of the Billy affair resulting in the dumping of the president, accordingly, still looks dim. It will have to assume truly horrendous proportions before the movers and shakers of the Democratic Party turn on Carter. As one of them put it: "My mother didn't raise me to be a kamikaze pilot."