THERE IS nothing inherently wrong with electing members of a governing body like a city council on an at-large basis or requiring runoffs if no candidate in a crowded field receives a majority of the votes. But in practice, some jurisdictions have used these devices effectively to disenfranchise minorities by diluting their voting power. The Justice Department has for years been litigating at-large cases and has succeeded in forcing the creation of single member districts so that minorities can win elections. Yesterday, the department filed its first suit challenging the equally unfair use of runoffs in the state of Georgia.

Runoffs are required by law in nine states. The Georgia statute was enacted just weeks before President Johnson signed the landmark 1964 Civil Rights Act and a year before the passage of the Voting Rights Act. Both federal laws were aimed at eliminating barriers to voting that had traditionally kept blacks from participating in the political process. At the time, only one out of four eligible blacks was registered to vote. The Justice Department now charges that in anticipation of the changes that were about to occur because of the strong new federal laws, Georgia legislators mandated runoffs in every primary and general election where the winner did not receive a majority of the votes. Time and again, the department's complaint alleges, blacks have finished first in multicandidate races, only to lose a runoff in which whites vote as a bloc. If this case is proved in court, jurisdictions where the runoffs have produced racially discriminatory results will have to abandon the practice; other jurisdictions will have to show that a "legitimate, non-racial, overriding governmental purpose would be served" by the retention of the system.

Some question has already been raised about the political impact of abandoning runoffs, and Republican officials in the South have predicted that their party will benefit by any change that produces more black nominees in the primaries. The law, however, is not concerned with partisan side-effects. It simply requires the states to treat citizens equally and to protect their exercise of the constitutional right to vote. If runoff requirements have been adopted by states for the same invidious reason as literacy tests and poll taxes, then this practice, like those earlier discriminatory requirements, should be prohibited. The suit against Georgia is a welcome challenge, affirming the federal government's responsibility to individual voters and to the maintenance of a fair and inclusive political process.