IF YOU CAN BELIEVE any of the high-minded and statesmanlike oratory that engulfed the Capitol last week at the formal opening of the 99th Congress, the members of the House and Senate are determined to take swift, sure and fearless action to deal with the budget deficit and other challenging federal issues.

If the members mean what they say (always an iffy proposition when dealing with Congress), there is a step they could take, surely and swiftly -- as early as tomorrow morning, in fact -- that would cure the basic illness at the root of so many of our governmental problems.

This step would be easy, painless and 100 percent guaranteed to end an historical anomaly and stop the craven kowtowing to interest groups that has created legislative gridlock, leaving Congress unable to take any significant action on any serious national concern.

Here's the solution to our problems: Every member of Congress should stand up tomorrow and swear an oath that this will be his or her last term. That single step would not only rid us of 535 people who have proven decisively over recent years that they are incapable of balancing a budget, writing a sensible tax code or anything else worthwhile. It would also eradicate a new and harmful strain of public official unknown to the Founding Fathers and to most of American history: the career congressman.

The 99th Congress, like its predecessors for the past 15 Congresses or so, is populated almost entirely by people who have either made congressional service a career or hope to do so. The average congressionl service of representatives today, for example, is around 12 years; for senators, considerably longer. It is routine for a member to stay in Congress a quarter century or more.

The resulting "petrification" of Congress, to use an apt term coined by political scientist Morris P. Fiorina, is precisely the opposite of what the architects of our system had in mind.

The Founding Fathers pictured a representative body composed of ordinary citizens taking a brief respite from real life to represent their neighbors.

The authors of the Constitution could have made the House of Representatives a continuing body, but they deliberately chose not to.

For most of American history, the people elected to the House have honored that choice. Through 1870, the average continuous House career was shorter than four years. As late as 1920, the figure was less than seven years.

Most of the truly great figures in the history of the House went back home at a point where the contemporary representative is still arranging the office furniture.

Daniel Webster served 2 1/2 House terms. Henry Clay, arguably the greatest House member ever, decided to resign after five terms but then relented and served one more. A promising freshman congressman from Illinois created such a furor in 1847 when he proposed running for a second term that his own party abandoned him; thus ended Abraham Lincoln's congressional service.

The first 75 Congresses were continually invigorated with new blood; until the realigning election of 1896, half or more of almost every new House was made up of freshman. As late as the 81st Congress, which convened in 1949, there were 160 freshman members -- just over 30 percent. In the 99th Congress, 9.4 percent are freshmen.

The men who wrote the Constitution designed the Senate to be the institutional memory of the federal government, but we know that they did not think of that body, either, as a career position. We know this because several of the Founding Fathers served in the Senate -- for one term or less.

Of the 26 members of the first Senate, only 10 ran for re-election. Of the eight who won, four resigned midway through the second term. None stood for a third term: the whole idea of serving more than 12 years was unthinkable.

Nowadays, in contrast, members shudder at the thought of serving fewer than a dozen years. Washington is their home and Congress is their job, and they have created a vast array of incumbent-protection devices, at taxpayer's expense, to see to it that they never have to go back to a real town and a job. With a career in mind, they live in abject fear of any interest group that might challenge their right to a lifetime of congressional pay and perquisites.

The result is a timid, isolated, and thoroughly unrepresentative corps of congressional professionals. "We're very far from the rest of the nation here," said retiring Sen. Howard Baker (R-Tenn.). "We live in our federal compound. The Capitol, our offices, the Shoreham, the Sheraton Park, the other hotels where you meet the same people day after day . . . . I wanted to get out of here because I knew I didn't know the country, these people I'm representing."

H. Douglas Price, the political scientist who has done pioneering work on the emergence of a "professional" Congress, suggests that one result of the career consciousness is that many able young members sort of sit around waiting for seniority to happen to them before they really do anything.

I saw this vividly last year on a campaign trip with Rep. Robin Tallon (D-S.C.), an amiable, earnest mediocrity who got to Congress in part because he had the good sense to live in the district once represented by Rita Jenrette's felon husband John.

Running for his second term, Tallon came right out and told voters in Myrtle Beach that "I haven't been able to do as much as I would have liked so far, but if I can build a career in the House, I can really be a power for this district." It is not exactly the Daniel Webster philosophy.

In sharp contrast to the Founding Fathers, members today routinely seek re- election, probably without a moment's thought. Fully 408 of the 435 voting House members ran for re-election in 1984 as did 29 of the 33 Senators whose terms expired. All but 19 of those incumbents won, assuring the sad reality that the new Congress will be a carbon copy of its listless, ineffectual predecessor.

Part of the reason the members all tend to run again and again and again is that they live with a snowballing campaign debt that an ex-member cannot raise money to pay off. "I've got a six-figure debt from (the) '82 (campaign)," Rep. Peter Kostmayer, a candid Pennsylvania Democrat, said last spring. "I can't afford not to run this time."

Mainly, though, today's member of Congress looks on his seat as his career. Indeed, many pass the job on to siblings, spouses or kids as if it were a family dry-cleaning business. This practice has brought us such legislative gems as Rep. Sala Burton (D- Calif.), whose only qualification for high public office is her status as widow of Rep. Phillip Burton -- himself a career House member.

During a serious constitutional debate in the last Congress, Burton contributed to the discussion by telling her colleages that the preamble to the Constitution contains the guarantee that "all men are created equal." That guarantee, of course, is contained in the Declaration of Independence.

"Well, she doesn't know anything about American history, but she's got a safe seat," one of her colleagues sighed. That's not a bad description of the average member of Congress today.

The legislative result of creeping careerism was crystalized perfectly last year by the long agony and eventual stalemate over legislation governing illegal immigration. Every member of Congress knew that the people wanted something done. The members talked a lot and actually passed bills -- but no law emerged. The whole matter was finally dropped in the heat of the election campaign. The members knew that any final vote might have angered some group or other that could terminate the dream of a lifetime job in the Capitol.

If the members of the 99th Congress were to take the career-ending oath tomorrow, there's a chance they would find the courage to act on immigration, the deficit, the tax code and other demanding problems. Even if they didn't, their departure would open the way for a 100th Congress filled with a whole team of genuine citizen-legislators (who would also be expected to take the oath).

One objection raised to this "throw-all-the bums-out" proposal might be that a Congress completely filled with freshmen would be even more dependent than the present crew on the congressional staff, one of the biggest and most hidebound of all Washington bureaucracies.

It's hard to imagine how anybody could depend more on staffers than the current members of Congress, but if this were to happen, there's a simple solution: make the staff take the one-more-term oath as well.

The members of the 99th Congress -- the vast majority of whom were members of the 98th, 97th, 96th, etc., Congresses as well -- have had their chance. They've failed. Can anybody honestly argue that these are the best 535 people we could find in this great country to run the legislature? Of course not. It's time for them to step aside and let 535 newcomers run the country. God knows they couldn't do any worse.