The Supreme Court yesterday upheld the legality of independent expenditures for presidential campaigns, a practice that allows the spending of millions of private dollars in what are supposed to be totally federally financed campaigns.

But the court's action yesterday does not resolve the controversy because it was accomplished by a 4-to-4 vote. Justice Sandra Day O'Connor produced the equally divided court when she disqualified herself from the case without explanation.

The tie vote affirms a lower court ruling striking down a $1,000 ceiling on expenditures by organizations not affiliated with a regular campaign. A three-judge U.S. District Court panel said the limitation violated the free speech rights of the independent organizations. Those independent groups spent $13.7 million in the 1980 elections touting their favorite candidates. About $11 million (mostly for Ronald Reagan) was spent in the general election, where private funds may not be spent by the candidates.

The practice was challenged by the Federal Elections Commission and by Common Cause, which sought enforcement of the $1,000 cap against several conservative organizations, including the Fund for a Conservative Majority and Americans for Change, which is headed by Sen. Harrison H. Schmitt (R-N.M.). Instead of enforcing the law, however, the panel struck it down.

A candidate's decision to forgo private funding, the panel said, "cannot bind his or her supporters outside the official campaign," whose own rights of expression are at stake.

As a result of the ruling, the groups were free to spend whatever they pleased in the 1980 elections. As a result of yesterday's court action, they may also be free to do the same in the 1984 elections because there are no cases currently on the horizon that might produce a clear Supreme Court opinion.

Common Cause yesterday expressed the hope that the $1,000 limit would be enforced by the FEC anyway. "The statute still forbids" the expenditures, Common Cause Chairman Archibald Cox said in a statement. "Common Cause will continue to press for enforcement of the statute and we assume the FEC will do the same."

An FEC spokesman said, however, that the agency was still assessing the Supreme Court action.

The conservatives, meanwhile, were delighted. "We are pleased that the Supreme Court has upheld the ability of individual Americans to participate in campaigns and the ability of all of us to run independent efforts on behalf of candidates," said Robert Heckman, chairman of the Fund for a Conservative Majority.