In 1789, as the nation's best and brightest pondered the intricacies of a national Constitution, Thomas Jefferson proposed placing a limit on the federal government's ability to go into debt.

But the concept of spending no more than you have appeared so self-evident, so imminently rational, that the forefathers omitted it from the Constitution. Almost 200 years later, the U.S. government is more than $1 trillion in debt.

Lawmakers here are seeking to correct the forefathers' omission by making Missouri the 32nd state to call for a constitutional convention to approve an amendment mandating a balanced federal budget.

The approval of 34 states is needed, but Missouri supporters think 32 will be enough to convince Congress that a convention is inevitable. The supporters reason that to avert a constitutional convention --which, once in session, can tinker with just about anything in the Constitution--federal lawmakers will scamper to approve a balanced-budget amendment and submit it to the states for ratification.

Missouri, a state undergoing a cash-flow crisis so severe that state income tax refunds are being delayed, has been hurt by the inflationary effects of the deficit, particularly high interest rates.

Many legislators from both parties say they have lost faith in the ability or willingness of President Reagan and the Congress to take corrective measures. They note that the president, who vowed as a candidate to balance the budget, now says the debt will grow by another $100 billion this year.

"If we don't do something there's not going to be a federal governmant at all," said Sen. Phillip Snowden, a Kansas City Democrat who will introduce a balanced budget resolution this week in the Senate. "Now it the deficit is over $100 billion, next year a projected $160 billion. It's just crazy."

Several previous attempts to approve balanced budget resolutions sailed through the Senate but died in the House at the hands of those who say they support a balanced budget but fear a constitutional convention might bring a wholesale onslaught on basic freedoms, or at the very least fragment the country over sensitive issues such as abortion or equal rights.

To avoid that problem, the Missouri resolution contains a caveat: If the convention is not limited to the balanced budget issue only, Missouri withdraws its support.

But the caveat hasn't converted everyone. While conceding that opposing a balanced federal budget is "like being against motherhood," Rep. Elmer (Lucky) Cantrell, a Democrat from St. Louis County and a voice for labor in the House, said he can't support any measure that includes a call for a convention.

And Lt. Gov. Kenneth Rothman agrees: "This is no time to take the ship of state into uncharted waters."