The American Bar Association convenes its annual convention in Chicago today under heavy pressure to rescind the abortion rights stand its House of Delegates passed last February.

Opponents of the stand are spending an estimated $50,000 on their campaign and have enlisted the aid of a professional pollster, the Roman Catholic archdiocese of Chicago and the dean of Notre Dame Law School, who wrote to the school's 5,000 alumni.

ABA abortion rights activists have struck back with the association's official machinery, cranking out about 15,000 letters to members across the nation urging them to stand firm. The 171,000-member Young Lawyers Division, the ABA's largest entity, has thrown its weight behind the current policy, as have groups of women lawyers around the nation.

The ABA has never seen such a firestorm of lobbying, protest and publicity.

In the months since the vote, 1,488 of the group's 350,000 members have resigned in protest, with threats from others to leave if the policy is not repealed. About 35 have joined up, citing the abortion stand, and nearly 400 members have written to express their support.

"The ABA is in a total paroxysm over this," one staff member said. "It is all anybody talks about. It is an obsession."

Last February, after two hours of emotional, sometimes acrimonious, debate, the ABA's governing body passed the abortion resolution by a vote of 238 to 106. The resolution recognized "the fundamental rights of privacy and equality guaranteed" by the Constitution and opposed "legislation or other governmental action that interferes" with the relationship between a pregnant woman and her physician.

While the House of Delegates, a representative body of 461 members, is the only group that can set ABA policy, opponents of the resolution have set their sights on the ABA Assembly, an often-ignored town meeting made up of any member who attends the convention and pays the registration fee of up to $250.

When the Assembly meets Monday, the antiabortion forces will introduce four resolutions aimed at reversing the present stand. Though the Assembly's vote is not binding, many argue that the House would have trouble ignoring its will when the House takes up abortion again Wednesday.

"Whoever wins there goes into the House of Delegates with a head of steam," said D.C. Bar President Sally Determan, a prime supporter of the current policy.

Whatever the outcome, the ABA Assembly can then take a second vote and force a referendum of the entire membership if it disagrees with the delegates' vote Wednesday.

The antiabortion forces have focused their efforts on passing a new resolution submitted by ABA Secretary-elect Anthony Palermo of New York. Palermo said it is "a neutrality stance" on an issue far too emotional and personal to ever find common ground in the diverse ABA.

But Washington, D.C., lawyer Estelle Rogers, a prime supporter of the current resolution, said there is no turning back. The ABA had an opportunity to adopt a neutral position last February, she said. But now reversal "would be viewed as a repudiation on the merits . . . and it would not change how strongly people feel."

Ironically, the ABA judicial screening committee is currently examining the qualifications of U.S. appeals court judge David H. Souter for the Supreme Court. Abortion is likely to be a major focus of his Senate confirmation hearings.

ABA officials have consistently denied that the committee examines the policy views of nominees. But Attorney General Dick Thornburgh has warned that the group's stance on one of "the most controversial, hot-button, highly emotional political issues of the day" could taint the ABA's appearance as a neutral evaluator.