WHAT'S HAPPENING to the abortion issue in Congress? Back in November 1980, when so many opponents of restriction on abortion were defeated by candidates who made their opposition to abortion an issue, the anti-abortion movement seemed to have unstoppable political momentum. Now it seems to be stalled. The Senate, when it adjourned Aug. 20, had declined to vote on anti-abortion measures sponsored by Sen. Jesse Helms (R- N.C.). Their chances of passage when Congress comes back Sept. 8 do not seem much greater.

One reason this has happened is that it is the anti- abortion forces who are trying to change the status quo. On Capitol Hill, as elsewhere, it is easier to prevent change from occurring than it is to make it happen. In the Senate, a minority large enough and determined enough can prevent Sen. Helms's proposals from being considered, and on this issue feelings are strong on both sides. In the past, the Senate has supported federal funding of abortions under many circumstances.

Another reason Mr. Helms's proposals are in trouble is the form in which he has presented them. He has used as his vehicle a bill to raise the debt ceiling, a measure that must be passed by Sept. 30 if the government is to pay its bills. He has at least three very different amendments:

* One is a bill -- not a constitutional amendment, just a bill -- that would declare that the fetus is a "person" under the Constitution. It would ban federal support of abortion.

* A second is the constitutional amendment sponsored by Sen. Orrin Hatch (R-Utah) that would give Congress and the states authority to restrict abortions.

* A third proposal is a statute barring federal courts from considering cases concerning voluntary school prayer. This is obviously an unrelated measure, and Sen. Helms is apparently trying to maximize support for the anti-abortion measures by tying them to a measure that few senators want to oppose.

It seems evident to us and, apparently, to quite a few senators as well that Sen. Helms is trying to make an end-run around the constitutional amendment process and is trying to make policy by gimmick on a delicate issue about which citizens on both sides have strong feelings. The Constitution should be changed only by the process the framers designed (on purpose) to be solemn and cumbersome -- by two-thirds votes in each house of Congress followed by ratification by 38 state legislatures -- not by simple majority vote in Congress. Nor should as important a measure as a constitutional amendment authorizing restrictions on abortion be passed as a piggyback measure on the strength of a necessary housekeeping measure like the debt ceiling bill or an apple-pie measure like the school prayer bill.

It is heartening that, on procedural matters, Sen. Helms has been unable to summon as many votes as the political popularity of the measures he is pressing might lead one to expect: evidently the procedural votes give senators who have doubts about his methods a chance of defeating them without seeming to stand squarely in opposition to his proposals on the merits. If, as seems likely, anti-abortion measures are not passed in this Congress, fervent opponents of abortion should blame not only the obduracy of their equally fervent opponents but the too-clever-by-half tactics of their own champions.