The president will soon be offered a compromise on the voting rights bill and with it an opportunity to improve his relations with the black community, to respond to moderates in his own party and to assume the leadership on an important civil rights issue. He should take it.

Extension of the Voting Rights Act has been the primary legislative objective of civil rights leaders this year. That law, parts of which are due to expire in August, has been extraordinarily effective in protecting the franchise in areas where racial discrimination had been the rule. It should be extended. The president favors extension of the law, but his support has been obscured in a bitter dispute over a change that was adopted by the House when it passed the extension bill on a vote of 389 to 24 last October.

The House bill provides that a voting system can be found to be discriminatory if the effect of that system is to exclude minorities from the political process. The Justice Department opposed this provision, arguing that litigants should have to prove that public officials intended to discriminate when they devised the voting system. An effects test, said department officials, would lead to racial quotas and proportional representation.

No one wanted such a result, and key members of the Senate Judiciary Committee have been working to amend the bill in order to meet some of the administration's objections. Over the last two weeks, Sens. Robert Dole and Edward Kennedy and Charles Mathias have hammered out a compromise that is expected to be offered to the full Judiciary Committee by Sen. Dole early this week. More than a dozen members of the committee have indicated they will support this version of the bill.

The key changes are designed to guarantee that plaintiffs must show that the totality of circumstances --not just the election results--prove discrimination. Further, the new bill would provide specifically that no group has a right to win elective office in numbers equal to its proportion in the population.

These changes in the bill should meet any legitimate objections raised by the administration. They provide assurance that civil rights groups and legislators ranging from liberal to quite conservative have made a good-faith effort to respond to the administration's concerns. The president has everything to gain by praising the compromise and urging prompt passage of the amended bill.