AT 2 O'CLOCK this afternoon, conferees on the Simpson-Mazzoli immigration reform bill will gather for one more attempt to save the measure before this Congress adjourns finally. The bill has survived a series of close calls. Any one of a number of controversial amendments could have killed it on the House floor, but it squeaked by with a five-vote margin last June. Supporters were also able to withstand the political pressures that threatened the bill at the time of both party conventions this summer. Last month, House and Senate conferees surprised almost everyone by working quickly and efficiently to devise compromises on the major issues in the bill: amnesty and employer sanctions. At the last minute though, the conference fell apart when members could not agree on the question of employment discrimination against aliens. Ten days ago, the bill was given up for dead.

Then, something unexpected happened. Some members of the conference, including the two principal sponsors, faced with the prospect of seeing years of work and compromise go down the drain, decided to make one last try to save the bill. A series of private meetings was held, and now language on the alien job rights provision has been written that is acceptable to Sen. Simpson and Rep. Mazzoli and to the author of the amendment, Rep. Barney Frank.

Because time is short, nothing is certain even if the conferees agree this afternoon. Neither the unions nor the big western growers are satisfied with provisions on temporary agricultural workers. Hispanic groups don't like employer sanctions, and some conservatives think the amnesty is too generous. A handful of senators could prevent a final vote before adjournment, and the president, who has promised to state his position on a veto before the House votes, could balk. But there has been such a sustained and remarkable good-faith effort by legislators of both parties to resolve important immigration problems that it would be criminal to see their cause lost now in the final hours of the session -- and to see this enormous legislative accomplishment destroyed.