ALTHOUGH THE Reagan administration has yet to decide what it thinks about the Voting Rights Act of 1965, several of its allies on Capitol Hill have concluded that the act should be extended for another 10 years. That's good news. But it is more than just that. It is also a demonstration that there is still some sensitivity in Congress to racial descrimination when its existence is carefully documented.

In this instance, the hearings on voting practices conducted by a House Judiciary subcommittee provided the necessary documentation. Witness after witness explained the various schemes that have been tried in some parts of the country to discourage minority voters from going to the polls or to minimize the political impact of the votes they cast. There were stories -- uncontradicted -- of voting registrars whose offices are suspiciously inconvenient to get to or open only very briefly, of sudden annexations by cities of suburban areas when black voters began to register in large numbers, of changes in election procedures designed to keep blacks out of office and of the moving of polling places on election eve in black areas.

Even as staunch a proponent of states' rights as Rep. Henry J. Hyde was persuaded by such testimony that further fedeal supervision over state election laws is justified -- as he wrote in last Sunday's op-ed page article "Why I Changed My Mind on the Voting Rights Act."

The evidence, of course, was always there, even when serious suggestions were made earlier this year that the Voting Rights Act be abolished or "extended" to cover the entire country. It was ignored then, just as was the fact that the act couldn't be extended nationwide because it already applied everywhere. Whether any particular state or locality has been subject to close federal scrutiny under its terms depends not on geographic location, as the act's opponents often imply, but on a past history of official discrimination.

The evidence also suggests that there are some provisions of the act that could be improved. The "escape" mechanism, for instance, is so cumbersome that few covered jurisdictions have been attempted to be released from the requirement that the pre-clear new election laws with the Department of Justice. But the trick here is to design a new mechanism that will free only those state and local governments that are prepared to comply with both the letter and the spirit of non-discriminatory voting requirements.

For those who still have doubts about the need to keep the key provisions of this major civil rights legislation on the books -- we have in mind some high officials in the Reagan administration and both candidates for governor of Virginia -- the testimony presented to the House subcommittee should be required reading. The record compiled thre makes it difficult for any fair-minded citizen to reach a conclusion different from that of Rep. Hyde: that the act should be extended with no impairment of its enforcement provisions.