Sign the bill, Mr. Reagan

AS President Reagan has zoomed into airports around the country these past several days to make last-minute campaign pitches for Republican senatorial candidates, he has played on his own personal popularity by telling voters, ``If you want to vote for me one more time, vote for [candidate's name inserted here].'' Now the President has an opportunity to return the favor to the voters: He can sign the Clean Water Act. It passed both houses of Congress unanimously: 408 to 0 in the House and 96 to 0 in the Senate.

It went to the White House for his signature last Saturday. Claiming the $18 billion bill is a ``budget-buster,'' he has threatened to veto it, despite the solid support it got from Congress, including the Republican-controlled Senate he has been invoking as a key player in keeping the ``Reagan revolution'' on course.

With Congress out of session, he can ``pocket-veto'' the bill by simply holding it unsigned for 10 working days after the date of its delivery to the White House; that is, until just after the election. Some Democrats and environmentalists are charging that the Republican Senate leadership stalled on getting the bill to the President to spare Republican congressional candidates the political heat that would be generated by the election-eve veto of such a popular bill.

A spokesman for the Senate secretary has insisted that the delay was caused by ``technical requirements.'' But in any case, it's clear that environmental legislation like this would not have such resounding support in Congress unless it had public support as well. The President ultimately signed the Superfund bill, which had similarly enthusiastic congressional support, after Congress, already well into overtime, threatened to stay in session to override a veto. That was not an option in this instance, given the realities of the election-year calendar.

But the 99th Congress, for all its conservatism and cost consciousness, has learned that strong environmental law is as important to the electorate as any element of ``the Reagan revolution.'' It is a lesson the President should learn, too.