A little-noticed federal court victory for Democrats in Indiana ironically has raised the possibility of nationwide legislative and congressional redistricting that could give the Republicans scores of additional seats, GOP leaders said today.

In the Dec. 13 decision, two of three judges on the special panel ruled that the districts used in the 1982 Indiana legislative elections had been drawn unconstitutionally because they did not reflect the political makeup of the state as a whole. They noted that Democratic candidates had collected more than 49 percent of the vote but won only 43 of 100 seats.

They agreed with Democratic Party attorneys that the Republicans in control of the state legislature had divided towns and other natural communities to minimize Democratic chances at the polls.

Two decades ago, the Supreme Court -- in its celebrated one-man, one-vote ruling -- outlawed schemes in which the number of people in each district vary widely. But, the high court has yet to say that concentrating a party's supporters in a few districts is unconstitutional.

The Indiana ruling now goes to the Supreme Court. If upheld, it could affect not only legislative but congressional districts. In 1984, Republicans won nearly half the popular vote in congressional races nationwide but won less than 42 percent of House seats.

Republicans "would certainly be the beneficiary" of a ruling that judged such discrepancies to be constitutionally suspect, Republican National Committee spokesman William Greener said today.

It is unclear how many state legislatures and congressional delegations would be affected if the ruling were applied nationwide, but Democrats are thought to have more to lose because they have a 251-to-182 majority in the House and control 28 of 50 state legislatures.

The ruling could have particular significance in California, where Republican politicians have complained for years of redistricting plans designed to weaken their growing suburban power.

Greener said the GOP will announce Wednesday a request that the Supreme Court consider the California situation along with the Indiana appeal.

California state assemblyman Don Sebastiani, a Republican who has helped lead a long, expensive fight against Democratic-drawn districts, said today he greeted the Indiana decision with "glee and joy and a prayer of thanks."

"We have heard for a long time that there are a lot of responsible members of the judiciary who feel gerrymandering should be unconstitutional," he said.

Gerrymandering is the time-honored American term, dating back to the early 19th century, for drawing election districts to the advantage of a particular party.

Indianapolis attorney William M. Evans, a former state legislator who represented the Indiana Republican Party before the three-judge panel, said the authors of the majority opinion -- U.S. District Court Judges James E. Noland and Gene E. Brooks -- indicated that they knew they were "making new law" with their decision.

Evans said they leaned heavily on a concurring opinion by Supreme Court Justice John Paul Stevens in a 1983 New Jersey redistricting case, Karcher v. Daggett. In his concurrence, Stevens suggested that using district lines to diminish a party's legislative strength would invite court review.

Evans said the two judges, both Democratic appointees, ruled that, given Indiana's almost evenly divided electorate, legislative districts should be reasonably competitive. The gap between the two parties' projected vote in a district -- based on past voting patterns -- should not be more than a 10 percent, they said.

The dissenting member of the panel, Judge Wilbur F. Pell Jr. of the 7th U.S. Circuit Court of Appeals, said little could be done about some voter concentrations, such as black Democrats in urban areas.

Pell, a Republican appointee, also noted that there was no significant discrepancy between the Democratic popular vote and Democratic seats in the state Senate, whose district lines were also overturned.

The panel agreed to let stand the results of the 1984 state elections but ordered the legislature to draw new lines for the 1986 elections and reserved the right to review the new boundaries.

Under federal rules, the Supreme Court cannot avoid hearing the Indiana case, although it may reject the Republican request to rule on the California situation at the same time.